--------------------------------------------------------------------------------
Prospectus

                                    XOMA Ltd.
                             6,000,000 Common Shares
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o    All of the common shares offered by this prospectus are being offered by
     Millennium Pharmaceuticals, Inc. through its wholly-owned subsidiary,
     mHoldings Trust, which is a party to an investment agreement with XOMA and
     has become one of our shareholders through the purchase of common shares
     under the investment agreement.

o    We have used and intend to continue to use the proceeds from our sale of
     common shares to the selling shareholders under the investment agreement
     principally for the development of products pursuant to our collaboration
     with Millennium.

o    To the extent shares are issued upon conversion of an outstanding
     convertible subordinated note, we will benefit from the resulting
     cancellation of indebtedness. The $5.0 million convertible subordinated
     note is convertible at our option into our common shares.

o    Millennium and mHoldings Trust will receive all of the proceeds of their
     sale of such common shares to you.

o    Our common shares are listed on the Nasdaq National Market under the symbol
     "XOMA." The last reported sale price for the common shares on May 20, 2003
     was $5.98 per share.

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     This investment involves a high degree of risk. Consider carefully the risk
factors beginning on page 4 of this prospectus before you invest.

     Millennium Pharmaceuticals, Inc. and its wholly-owned subsidiary, mHoldings
Trust, are underwriters with respect to all of the common shares they purchase
under the investment agreement with XOMA and which are offered for sale under
this prospectus.

                              ____________________

     Neither the SEC nor any state securities commission has approved these
securities or determined that this prospectus is accurate or complete. Any
representation to the contrary is a criminal offense.

                              ____________________

                  The date of this prospectus is June 6, 2003.







                                TABLE OF CONTENTS




                                                 Page                                                      Page
                                                 ----                                                      ----


                                                          
Prospectus Summary................................1          Use Of Proceeds..................................19
Risk Factors......................................4          Selling Shareholders.............................20
Incorporation Of Information We File                         Description Of Share Capital.....................23
  With the SEC...................................16          Plan Of Distribution.............................26
Special Note Regarding Forward-Looking                       Legal Opinion....................................27
  Statements.....................................17          Experts..........................................28
Price Range Of Common Shares And Dividend                    Where You Can Get More Information...............28
  Information ...................................18









                                      -i-



                               PROSPECTUS SUMMARY

XOMA

     We are a biopharmaceutical company that develops and manufactures
recombinant antibodies and other protein products to treat cancer, immunological
and inflammatory disorders, and infectious diseases. Our current product
development programs include:

o    Raptiva(TM)(Efalizumab, formerly Xanelim(TM)) is a humanized anti-CD11a
     monoclonal antibody developed to treat immune system disorders. In February
     of 2003, Genentech received formal acknowledgement from the U.S. Food and
     Drug Administration that it had received the December 2002 submission of
     the Biologics License Application for marketing approval of Raptiva(TM)in
     patients with moderate-to-severe plaque psoriasis. The BLA filing is based
     on efficacy and safety data from three Phase III studies. Genentech has
     projected a 10-month regulatory review period for Raptiva(TM)in the U.S.
     with FDA action expected in late 2003. Genentech has granted Serono S.A.
     exclusive marketing rights to Raptiva(TM)outside the U.S. and Japan. In
     February of 2003, Serono announced the filing of an application for
     European Union marketing approval of Raptiva(TM)in moderate-to-severe
     plaque psoriasis.

     In 2002, Genentech and we initiated a Phase II clinical study of
     Raptiva(TM) in patients suffering from rheumatoid arthritis. In May of
     2003, Genentech and we announced our decision to terminate this and a
     follow-on study testing of Raptiva(TM) in patients suffering from
     rheumatoid arthritis based on an evaluation by an independent Data Safety
     Monitoring Board that suggested no overall net clinical benefit in patients
     receiving the study drug. In January of 2003, we announced initiation of a
     Phase II study to evaluate Raptiva(TM) as a possible treatment for patients
     with psoriatic arthritis. Genentech and we continue to assess additional
     indications for Raptiva(TM), and this study is ongoing.

o    Two of Millennium Pharmaceuticals, Inc.'s biotherapeutic agents are being
     developed for certain vascular inflammation indications pursuant to a
     collaboration agreement with Millennium that was announced in November of
     2001. Ongoing preclinical testing will be evaluated in determining plans
     for clinical testing.

o    ONYX-015, also known as CI-1042, developed by Onyx Pharmaceuticals, Inc.,
     is a therapeutic tumor-selective, modified adenovirus genetically
     engineered to destroy cancer cells. In 2002, under a strategic process
     development and manufacturing alliance with Onyx, we scaled up production
     to 500-liter fermentation scale and improved the manufacturing process for
     ONYX-015. In January of 2003, Onyx announced the suspension of development
     activities related to ONYX-015 until it successfully engages a marketing
     partner.

o    NEUPREX(R), also known as rBPI21, is a genetically-engineered fragment of a
     particular human protein. We completed a Phase III efficacy clinical trial
     in 1999, testing NEUPREX(R) in severe pediatric meningococcemia, but the
     data from the trial were determined not to be sufficient to file for
     regulatory approval. Further development of this product is continuing
     under a license agreement with a division of Baxter Healthcare Corporation,
     and a Phase II study testing NEUPREX(R) in Crohn's disease completed
     enrollment in November of 2002 but results are not yet known. Plans for
     further development, including potentially gaining access to additional
     resources by collaborating with another pharmaceutical company, are being
     pursued with Baxter.

o    ING-1 is a Human Engineered(TM)recombinant monoclonal antibody that binds
     with high affinity to an antigen expressed on epithelial cell cancers
     (breast, colorectal, prostate and others) that is designed to destroy
     cancer cells by recruiting the patient's own immune system. Enrollment has
     been completed in two Phase I studies testing intravenous administration in
     advanced adenocarcinoma patients, which showed safety and tolerability
     results that supported further clinical development. An additional Phase I
     study with subcutaneous administration is ongoing. Further product
     development efforts and a decision on future collaborative




     arrangements will be determined based on the results of these studies. The
     ING-1 monoclonal antibody incorporates our patented Human
     Engineering(TM)technology, designed to reduce immunogenicity.

o    BPI-derived anti-angiogenic compounds with potential application for
     treating retinal disorders are being developed by us. Results of in vitro
     and in vivo studies conducted by Joslin Diabetes Center at Harvard
     University, presented in April of 2001 and published in February of 2002,
     showed that compounds derived from BPI inhibit the function of multiple
     growth factors involved in blood vessel formation and angiogenesis in the
     retina while sparing key retinal cells (pericytes). These data suggest that
     these compounds may have potential for treating retinal disorders. We are
     conducting further research together with Joslin.

o    Another BPI-derived topical anti-infective compound is in preclinical
     testing, the results of which will be evaluated in determining plans for
     clinical testing.

     We have experienced significant losses and, as of March 31, 2003, we had an
accumulated deficit of approximately $554.0 million. For the year ended December
31, 2002 and the three months ended March 31, 2003, we had a net loss of
approximately $33.2 million, or $0.47 per common share (basic and diluted) and
$13.1 million, or $0.18 per common share (basic and diluted), respectively.

     Based on current spending levels, anticipated revenues, debt financing
provided by Genentech for our share of Raptiva(TM) development and marketing
costs, and financing commitments from Millenium under the collaborative
agreement between the companies, we estimate we have sufficient cash resources
to meet our operating needs through at least the end of 2004. We continue to
evaluate strategic alliances, potential partnerships and financing arrangements
which would further strengthen our competitive position and provide additional
funding. We cannot predict whether or when any such alliances, partnerships or
arrangements will be consummated or whether additional funding will be available
when required and on terms acceptable to us.

Material Terms of Investment Agreement

     On November 26, 2001, Millennium and we entered into an investment
agreement which committed Millennium to purchase, at our option and subject to
the conditions described in the following paragraph, up to $50.0 million worth
of our common shares over the 30 months following the effective date of the
investment agreement. Of the up to $50.0 million worth of our common shares,
$5.0 million worth (and accrued interest) may be issued at our option upon
conversion of a convertible subordinated note already issued to Millennium, the
entire principal amount of which is currently outstanding. On December 18, 2002,
Millenium purchased approximately 1.4 million of our common shares for $7.5
million to satisfy, in part, its obligation under the investment agreement. On
May 16, 2003, we and Millennium agreed to delay the maturity of the $5.0 million
convertible subordinated note until February 26, 2004 and to adjust the timing
of Millenium's obligation to purchase the remaining $37.5 million worth of our
common shares. At six subsequent closings over the following 21 months, we may
issue up to $4.0 million, $9.0 million, $7.0 million, $6.0 million, $6.0 million
and $5.5 million worth of our common shares, respectively. At each closing, the
precise number of shares to be purchased by Millennium will be determined using
a formula based on the average of certain sale prices per common share as
reported on the Nasdaq National Market for a specified period of time prior to
the applicable closing date (subject to certain adjustments and limitations).
The formula is intended to reflect the current market price per common share at
the time of each closing, without any discount or premium.

     The obligations of Millennium to purchase the common shares that we wish to
sell at each closing will be subject to customary closing conditions, including
the delivery of legal opinions and certificates from our officers and updated
financial information, the continued listing of our common shares on the Nasdaq
National Market or the New York or American Stock Exchanges, the continued
effectiveness of the registration statement that includes this prospectus and
the continuation of our collaboration agreement with Millennium.

     We have agreed to register the resale of the common shares that we may sell
to Millennium at each closing and the common shares that we may issue to
Millennium upon conversion of the convertible debt. The registration statement
that includes this prospectus is intended to satisfy these registration
obligations. We will


                                      -2-


consummate the first direct sale of common shares to Millennium after the
registration statement that includes this prospectus is declared effective.

     The 6,000,000 shares registered under the registration statement that
includes this prospectus would have represented 7.8% of our outstanding common
shares as of May 20, 2003, after giving effect to their issuance. Based on the
current market price of our common shares, the investment agreement gives us the
option to require the selling shareholders to purchase an aggregate of up to
approximately 7.1 million common shares (assuming conversion of the convertible
subordinated note) for $42.5 million, in addition to the 1.4 million common
shares already purchased.

Material Terms of Convertible Subordinated Note

     In connection with the investment agreement, we issued to Millennium a $5.0
million convertible subordinated note. The principal of the convertible
subordinated note is due and payable in a single installment on February 26,
2004.

     The principal and accrued interest on the convertible subordinated note may
be converted in whole (but not in part) at our election upon maturity into our
common shares. The number of shares into which the convertible subordinated note
may be converted will be determined using a formula based on the average of
certain sale prices per common share as reported on the Nasdaq National Market
for a specified period of time prior to the conversion date (subject to certain
adjustments and limitations). The formula is intended to reflect the current
market price per common share at the time of conversion, without any discount or
premium. Based on the current market price of our common shares, we would be
entitled to issue an aggregate of approximately 0.84 million common shares in
full payment of the convertible subordinated notes.

     If we do not elect to convert the convertible subordinated note into common
shares, all outstanding principal and all accrued interest must be paid to
Millennium in cash on the maturity date, unless otherwise agreed.

     In addition to customary restrictions on our ability to convert, we will
not be entitled to convert any portion of the convertible subordinated note or
the accrued interest unless there is on the conversion date an effective
registration statement covering resale of all of the common shares into which
the principal of the convertible note and all accrued interest would convert. If
this is not the case at any time prior to its maturity date, then the
convertible subordinated note will remain outstanding until its maturity date
and, if no effective registration statement is then in place, we will be
required to repay all outstanding principal and accrued interest in cash on the
maturity date. The registration statement that includes this prospectus is
intended to satisfy these registration obligations.


                                      -3-






                                  RISK FACTORS

     You should carefully consider the following factors and other information
in this prospectus before deciding to invest in our common shares. You should
also consider carefully the other information contained, or incorporated by
reference, in this prospectus. The actual results of our business could differ
materially from those described as a result of these risk factors. In such case,
the trading price of our common shares could decline, and you may lose all or
part of the money you paid to buy our common shares.

Risks Relating To Our Business

None Of Our Therapeutic Products Have Received Regulatory Approval; If Our
Products Do Not Receive Regulatory Approval, Neither We Nor Our Third Party
Collaborators Will Be Able To Manufacture And Market Them

     Even our most advanced therapeutic product has not received regulatory
approval. Our products cannot be manufactured and marketed in the United States
and other countries without required regulatory approvals. The United States
government and governments of other countries extensively regulate many aspects
of our products, including:

     o    testing

     o    manufacturing

     o    promotion and marketing and

     o    exporting.

     In the United States, the FDA regulates pharmaceutical products under the
Federal Food, Drug, and Cosmetic Act and other laws, including, in the case of
biologics, the Public Health Service Act. At the present time, we believe that
our products will be regulated by the FDA as biologics. The FDA has announced
that it is consolidating its responsibility for reviewing new pharmaceutical
products into its Center for Drug Evaluation and Research, the body that
currently reviews drug products, combining that operation with part of its
biologics review operation, the Center for Biologics Evaluation and Research.
Because implementation of this plan may not be complete, we do not know when or
how this change will affect us. State regulations may also affect our proposed
products.

     The FDA has substantial discretion in both the product approval process and
manufacturing facility approval process and, as a result of this discretion and
uncertainties about outcomes of testing, we cannot predict at what point, or
whether, the FDA will be satisfied with our or our collaborators' submissions or
whether the FDA will raise questions which may be material and delay or preclude
product approval or manufacturing facility approval. As we accumulate additional
clinical data, we will submit it to the FDA, which may have a material impact on
the FDA product approval process.

     Our potential products will require significant additional research and
development, extensive preclinical studies and clinical trials and regulatory
approval prior to any commercial sales. This process is lengthy, often taking a
number of years, and expensive. As clinical results are frequently susceptible
to varying interpretations that may delay, limit or prevent regulatory
approvals, the length of time necessary to complete clinical trials and to
submit an application for marketing approval for a final decision by a
regulatory authority varies significantly. As a result, it is uncertain whether:

     o    our future filings will be delayed



                                      -4-


     o    our studies will be successful

     o    we will be able to provide necessary additional data

     o    our future results will justify further development or

     o    we will ultimately achieve regulatory approval for any of these
          products.

         For example,

     o    in 1996, we and Genentech began testing Raptiva(TM)(Efalizumab,
          formerly Xanelim(TM)) in patients with moderate-to-severe psoriasis.
          In April of 2002, we and Genentech announced that a pharmacokinetic
          study conducted on Raptiva(TM)comparing XOMA-produced material and
          Genentech-produced material did not achieve the pre-defined
          statistical definition of comparability, and the FDA requested that
          another Phase III study be completed before the filing of a Biologics
          License Application for Raptiva(TM), delaying the filing of a
          Biologics Licensing Application with the FDA for Raptiva(TM)beyond the
          previously-planned time frame of summer 2002. In September of 2002, we
          and Genentech announced the results of the additional Phase III study
          which achieved its primary efficacy endpoint. In December of 2002,
          Genentech submitted a Biologics License Application for Raptiva(TM)for
          the treatment of moderate-to-severe plaque psoriasis, which was
          accepted by the FDA in February of 2003. Genentech has projected a
          10-month regulatory review period, which could potentially lead to FDA
          action in late 2003. However, we do not yet know what issues the FDA
          may raise with respect to efficacy or safety of the drug or other
          elements of the application. In March 2003, we announced completion of
          enrollment in a Phase II study of Raptiva(TM)in patients suffering
          from rheumatoid arthritis. In May of 2003, we and Genentech announced
          our decision to terminate Phase II testing of Raptiva(TM)in patients
          suffering from rheumatoid arthritis based on an evaluation by an
          independent Data Safety Monitoring Board that suggested no overall net
          clinical benefit in patients receiving the study drug. We have also
          announced the initiation of enrollment in a Phase II study of
          Raptiva(TM)as a possible treatment for patients with psoriatic
          arthritis. We do not know whether or when any such testing will
          demonstrate product safety and efficacy in these patient populations
          or result in regulatory approval.

     o    in December of 1992, we began human testing of our NEUPREX(R)product,
          a genetically-engineered fragment of a particular human protein, and
          have licensed certain worldwide rights to Baxter. In April of 2000,
          members of the FDA and representatives of XOMA and Baxter discussed
          results from the Phase III trial that tested NEUPREX(R)in pediatric
          patients with a potentially deadly bacterial infection called
          meningococcemia, and senior representatives of the FDA indicated that
          the data presented were not sufficient to support the filing of an
          application for marketing approval at that time. Because neither we
          nor Baxter have generated any additional data or completed any further
          analysis, we do not know whether we will be able to supply such
          additional data. If we conduct an additional trial to provide the
          requested additional data, we will not know whether the results will
          be adequate for approval until the trial has been completed and the
          resulting data reviewed by the FDA. In November of 2002, Baxter
          completed enrollment in a Phase II study with NEUPREX(R)in Crohn's
          disease patients, but because we do not know the results, we do not
          know whether the results will justify further development.

     Given that regulatory review is an interactive and continuous process, we
maintain a policy of limiting announcements and comments upon the specific
details of the ongoing regulatory review of our products, subject to our
obligations under the securities laws, until definitive action is taken.



                                      -5-


Because All Of Our Products Are Still In Development, We Will Require
Substantial Funds To Continue; We Cannot Be Certain That Funds Will Be Available
And, If Not Available, We May Have To Take Actions Which Could Adversely Affect
Your Investment

     If adequate funds are not available, we may have to dilute or otherwise
adversely affect the rights of existing shareholders, curtail or cease
operations or, in extreme circumstances, file for bankruptcy protection. We have
spent, and we expect to continue to spend, substantial funds in connection with:

     o    research and development relating to our products and production
          technologies

     o    expansion of our production capabilities

     o    extensive human clinical trials and

     o    protection of our intellectual property.

     Based on current spending levels, anticipated revenues, debt financing
provided by Genentech for our share of Raptiva(TM) development and marketing
costs, and financing commitments from Millennium under the collaborative
agreement between the companies, we estimate we have sufficient cash resources
to meet our operating needs through at least the end of 2004. However, to the
extent we experience changes in the timing or size of expenditures or
unanticipated expenditures, or if our collaborators do not meet their
obligations to us or anticipated revenues otherwise do not materialize, these
funds may not be adequate for this period. As a result, we do not know whether:

     o    operations will generate meaningful funds

     o    additional agreements for product development funding can be reached

     o    strategic alliances can be negotiated or

     o    adequate additional financing will be available for us to finance our
          own development on acceptable terms, if at all.

     Cash balances and operating cash flow are influenced primarily by the
timing and level of payments by our licensees and development partners, as well
as by our operating costs.

     Specifically, although changes in spending on Raptiva(TM) should not impact
liquidity due to our financing arrangement with Genentech and FDA approval of
Raptiva(TM) would generally be expected to improve operating cash flow to the
extent of our share of operating profits, if any, from sales of Raptiva(TM) in
the U.S., such approval will also require repayment in cash, shares or deferred
repayment of up to $40.0 million of amounts owed to Genentech (approximately
$71.0 million under both loan agreements as of March 31, 2003). In addition, any
delays in the review by the FDA of the Biologics License Application for
Raptiva(TM) may have a material impact on our cash flow and on our ability to
raise new funding on acceptable terms.

The Financial  Terms Of Some Of Our Existing Collaborative
Arrangements Could Result In Dilution Of Our Share Value

     We have financed, and anticipate continuing to finance, our most
significant development program, Raptiva(TM), principally by borrowing from
Genentech, and this debt is convertible at our option into our common shares
with the conversion price to be calculated at the time of payment based on the
fair market value at the time of the election. The outstanding amount of such
convertible debt as of March 31, 2003 was approximately



                                      -6-


$67.4 million. This debt will come due at the earlier of (a) April of 2005,
except for advances made after April 2003 in which case payment will be due on
the second anniversary of the date of any such advances or (b) within 90 days
after first product approval (which could be before the end of 2003). Unless we
secure substantial alternative financing, it is likely that some or all of this
debt, as well as some or all of any convertible debt issued in the future as
part of this financing arrangement, will be converted into equity when it comes
due rather than be repaid in cash, resulting in the issuance of additional
common shares.

     Our financing arrangement with Millennium includes a $5.0 million
convertible note we issued to Millennium in November of 2001, which comes due in
February of 2004 and may be converted into common shares at that time. In
addition, we have the option to issue up to $37.5 million worth of common shares
to Millennium over the next 21 months. The total amount issuable in 2003 is
$13.0 million. The number of shares to be issued will be based on the conversion
price at the time of conversion.

     These arrangements, as well as future arrangements we may enter into with
similar effect, could result in dilution in the value of our shares.

Because All Of Our Products Are Still In Development, We Have Sustained Losses
In The Past And We Expect To Sustain Losses In The Future

     We have experienced significant losses and, as of March 31, 2003, we had an
accumulated deficit of $554.0 million.

     For the quarter ended March 31, 2003, we had a net loss of approximately
$13.1 million, or $0.18 per common share (basic and diluted). For the year ended
December 31, 2002, we had a net loss of approximately $33.2 million, or $0.47
per common share (basic and diluted). We expect to incur additional losses in
the future, primarily due to increased expenses on Raptiva(TM) and on the
Millennium collaboration, as well as lower licensing and contract services
revenue.

     Our ability to make profits is dependent in large part on obtaining
regulatory approval for our products and entering into agreements for product
development and commercialization, both of which are uncertain. Our ability to
fund our ongoing operations is dependent on the foregoing factors and on our
ability to secure additional funds. Because all of our products are still in
development, we do not know whether we will ever make a profit or whether cash
flow from future operations will be sufficient to meet our needs.

If Third Party Collaborators Do Not Successfully Develop And
Market Our Products, We May Not Be Able To Do So On Our Own

     Our financial resources and our marketing experience and expertise are
limited. Consequently, we depend to a large extent upon securing the financial
resources and marketing capabilities of third parties with whom we collaborate.

     o    In April of 1996, we and Genentech entered into an agreement whereby
          we agreed to co-develop Genentech's humanized monoclonal antibody
          product Raptiva(TM). In April of 1999, the companies extended and
          expanded the agreement. In March of 2003, the companies further
          expanded the agreement.

     o    In January of 2000, we licensed the worldwide rights to all
          pharmaceutical compositions containing a particular human protein for
          treatment of meningococcemia and additional potential future human
          clinical indications to Baxter.



                                      -7-


     o    In January of 2001, we entered into a strategic process development
          and manufacturing alliance with Onyx Pharmaceuticals, Inc. pursuant to
          which we are scaling up production to commercial volume to manufacture
          one of Onyx's cancer products.

     o    In November of 2001, we entered into a collaboration with Millennium
          Pharmaceuticals, Inc. to develop two of Millennium's products for
          certain vascular inflammation indications.

     Because our collaborators are independent third parties, they may be
subject to different risks than we are and have significant discretion in
determining the efforts and resources they will apply. We do not know whether
Genentech, Baxter, Onyx or Millennium will successfully develop or market any of
the products we are collaborating on.

     Even when we have a collaborative relationship, other circumstances may
prevent it from resulting in successful development of marketable products.
Specifically, in January of 2003, Onyx announced suspension of development
activities, including manufacturing, related to the product that is the subject
of our alliance, while Onyx seeks a marketing partner for the product to enable
it to reinitiate development, and we are not involved in assisting Onyx in this
process. Because these efforts are on-going, we do not know whether any
additional partner will be found. In addition, in March 2003, we announced that
we and Baxter would be seeking an additional company to bring development
resources and expertise to support Neuprex(TM) development. We do not know
whether we will be successful in securing such an additional company, and if we
are not, our failure to do so could have an adverse impact on clinical
development activities. Also, in June of 1999, we licensed certain
genetically-engineered fragments of a particular human protein to Allergan Inc.
to treat bacterial ophthalmic infections. In May of 2000, following successful
product testing at Allergan, we expanded the collaboration. In November of 2000,
Allergan advised us that for internal economic reasons they planned to
discontinue development of ophthalmic anti-infective products derived from this
protein.

     Although we continue to evaluate additional strategic alliances and
potential partnerships, we do not know whether or when any such alliances or
partnerships will be entered into.

Because We Have No History Of Profitability And Because The Biotechnology Sector
Has Been Characterized By Highly Volatile Stock Prices, Announcements We Make
And General Market Conditions For Biotechnology Stocks Could Result In A Sudden
Change In The Value Of Our Common Shares

     As a biopharmaceutical company, we have experienced significant volatility
in our common shares. Fluctuations in our operating results and general market
conditions for biotechnology stocks could have a significant impact on the
volatility of our common share price. From December 31, 2001 through May 20,
2003, our share price has ranged from a high of $12.19 to a low of $2.84. On May
20, 2003, the last reported sale price of the common shares as reported on the
Nasdaq National Market was $5.98 per share. Factors contributing to such
volatility include, but are not limited to:

     o    results of preclinical studies and clinical trials,

     o    information relating to the safety or efficacy of our products,

     o    developments regarding regulatory filings,

     o    announcements of new collaborations,

     o    failure to enter into collaborations,



                                      -8-


     o    developments in existing collaborations,

     o    our funding requirements and the terms of our financing arrangements,

     o    announcements of technological innovations or new indications for our
          therapeutic products,

     o    government regulations,

     o    developments in patent or other proprietary rights,

     o    the number of shares outstanding,

     o    the number of shares trading on an average trading day,

     o    announcements regarding other participants in the biotechnology and
          pharmaceutical industries, and

     o    market speculation regarding any of the foregoing.

Because Many Of The Companies We Do Business With Are Also In The Biotechnology
Sector, The Volatility Of That Sector Can Affect Us Indirectly As Well As
Directly

     The same factors that affect us directly because we are a biotechnology
company can also adversely impact us indirectly by affecting the ability of our
collaborators, partners and others we do business with to meet their obligations
to us or our ability to realize the value of the consideration provided to us by
these other companies. For example, in connection with our licensing transaction
with MorphoSys AG, MorphoSys has announced that it has exercised its option to
pay a portion of the license fee owed to us in the form of equity securities of
MorphoSys. We have only recently received these shares and the future value of
these shares is subject both to market risks affecting our ability to realize
the value of these shares and more generally to the business and other risks to
which the issuer of these shares is subject. Since the date of MorphoSys'
election on October 23, 2002, the per share closing price for MorphoSys shares
has ranged between approximately $4.64 to $15.20, which demonstrates the
volatility of these shares in the current market.

If Any Of Our Products Receives Regulatory Approval, We May Not Be Able To
Increase Existing Or Acquire New Manufacturing Capacity Sufficient To Meet
Market Demand

     Because we have never commercially introduced any pharmaceutical products
and none of our products have received regulatory approval, we do not know
whether the capacity of our existing manufacturing facilities can be increased
to produce sufficient quantities of our products to meet market demand. Also, if
we need additional manufacturing facilities to meet market demand, we cannot
predict that we will successfully obtain those facilities because we do not know
whether they will be available on acceptable terms. In addition, any
manufacturing facilities acquired or used to meet market demand must meet the
FDA's quality assurance guidelines.

Because We Do Not And Cannot Currently Market Any Of Our Products For Commercial
Sale, We Do Not Know Whether There Will Be A Viable Market For Our Products

     Even if we receive regulatory approval for our products and we or our third
party collaborators successfully manufacture them, our products may not be
accepted in the marketplace. For example, physicians and/or patients may not
accept a product for a particular indication because it has been biologically
derived (and not



                                      -9-


discovered and developed by more traditional means) if no biologically-derived
products are currently in widespread use in that indication, as is currently the
case with psoriasis. Consequently, we do not know if physicians or patients will
adopt or use our products for their approved indications.

If Our And Our Partners' Patent Protection For Our Principal Products And
Processes Is Not Enforceable, We May Not Realize Our Profit Potential

     Because of the length of time and the expense associated with bringing new
products to the marketplace, we and our partners hold and are in the process of
applying for a number of patents in the United States and abroad to protect our
products and important processes and also have obtained or have the right to
obtain exclusive licenses to certain patents and applications filed by others.
However, the patent position of biotechnology companies generally is highly
uncertain and involves complex legal and factual questions, and no consistent
policy regarding the breadth of allowed claims has emerged from the actions of
the U.S. Patent and Trademark Office with respect to biotechnology patents.
Legal considerations surrounding the validity of biotechnology patents continue
to be in transition, and historical legal standards surrounding questions of
validity may not continue to be applied, and current defenses as to issued
biotechnology patents may not in fact be considered substantial in the future.
These factors have contributed to uncertainty as to:

     o    the degree and range of protection any patents will afford against
          competitors with similar technologies

     o    if and when patents will issue

     o    whether or not others will obtain patents claiming aspects similar to
          those covered by our patent applications or

     o    the extent to which we will be successful in avoiding infringement of
          any patents granted to others.

     The Patent Office has issued approximately 63 patents to us related to our
products based on human bactericidal permeability-increasing protein, which we
call BPI, including novel compositions, their manufacture, formulation, assay
and use. In addition, we are the exclusive licensee of BPI-related patents and
applications owned by New York University and Incyte Pharmaceuticals Inc. The
Patent Office has also issued nine patents to us related to our bacterial
expression technology.

     If certain patents issued to others are upheld or if certain patent
applications filed by others issue and are upheld, we may require licenses from
others in order to develop and commercialize certain potential products
incorporating our technology or we may become involved in litigation to
determine the proprietary rights of others. These licenses, if required, may not
be available on acceptable terms, and any such litigation may be costly and may
have other adverse effects on our business, such as inhibiting our ability to
compete in the marketplace and absorbing significant management time.

     Due to the uncertainties regarding biotechnology patents, we also have
relied and will continue to rely upon trade secrets, know-how and continuing
technological advancement to develop and maintain our competitive position. All
of our employees have signed confidentiality agreements under which they have
agreed not to use or disclose any of our proprietary information. Research and
development contracts and relationships between us and our scientific
consultants and potential customers provide access to aspects of our know-how
that are protected generally under confidentiality agreements. These
confidentiality agreements may not be honored or may not be enforced by a court.
To the extent proprietary information is divulged to competitors or to the
public generally, such disclosure may adversely affect our ability to develop or
commercialize our products by giving others a competitive advantage or by
undermining our patent position.



                                      -10-


Protecting Our Intellectual Property Can Be Costly And
Expose Us To Risks Of Counterclaims Against Us

     We may be required to engage in litigation or other proceedings to protect
our intellectual property. The cost to us of this litigation, even if resolved
in our favor, could be substantial. Such litigation could also divert
management's attention and resources. In addition, if this litigation is
resolved against us, our patents may be declared invalid, and we could be held
liable for significant damages. In addition, if the litigation included a claim
of infringement by us of another party's patent that was resolved against us, we
or our collaborators may be enjoined from developing, manufacturing, selling or
importing products, processes or services without a license from the other
party.

Other Companies May Render Some Or All Of
Our Products Noncompetitive Or Obsolete

     Developments by others may render our products or technologies obsolete or
uncompetitive. Technologies developed and utilized by the biotechnology and
pharmaceutical industries are continuously and substantially changing.
Competition in the areas of genetically-engineered DNA-based and antibody-based
technologies is intense and expected to increase in the future as a number of
established biotechnology firms and large chemical and pharmaceutical companies
advance in these fields. Many of these competitors may be able to develop
products and processes competitive with or superior to our own for many reasons,
including that they may have:

     o    significantly greater financial resources

     o    larger research and development and marketing staffs

     o    larger production facilities

     o    entered into arrangements with, or acquired, biotechnology companies
          to enhance their capabilities or

     o    extensive experience in preclinical testing and human clinical trials.

     These factors may enable others to develop products and processes
competitive with or superior to our own or those of our collaborators. In
addition, a significant amount of research in biotechnology is being carried out
in universities and other non-profit research organizations. These entities are
becoming increasingly interested in the commercial value of their work and may
become more aggressive in seeking patent protection and licensing arrangements.

     Furthermore, positive or negative developments in connection with a
potentially competing product may have an adverse impact on our ability to raise
additional funding on acceptable terms. For example, if another product is
perceived to have a competitive advantage, or another product's failure is
perceived to increase the likelihood that our product will fail, then investors
may choose not to invest in us on terms we would accept or at all.

     Without limiting the foregoing, we are aware that:

     o    Biogen Inc. has announced that the FDA has approved Amevive(R)to treat
          moderate-to-severe chronic plaque psoriasis in adult patients who are
          candidates for systematic therapy or phototherapy;



                                      -11-


     o    Centocor Inc., a unit of Johnson & Johnson, has announced that it has
          tested its rheumatoid arthritis and Crohn's disease drug, Remicade(R),
          in psoriasis showing clinical benefits (and it has been announced that
          the drug has shown promising results in patients with psoriatic
          arthritis);

     o    it has been announced that Amgen Inc. tested its rheumatoid arthritis
          and psoriatic arthritis drug, Enbrel(R), in a Phase III clinical trial
          in patients with moderate-to-severe plaque psoriasis, meeting the
          primary endpoint and all secondary endpoints, that the primary and key
          secondary endpoints were met in a second Phase III trial, and that
          filing for regulatory approval with the FDA for this medication is
          expected in 2003;

     o    MedImmune, Inc. has completed enrollment in three Phase II trials to
          evaluate its anti-T cell monoclonal antibody in psoriasis;

     o    GenMab A/S has announced that its investigational new drug application
          for HuMax-CD4 for psoriasis has been cleared through the FDA to
          initiate a Phase II study;

     o    Abbott Laboratories has announced the commencement of a Phase II
          psoriasis trial and Phase III psoriatic arthritis trial of its
          rheumatoid arthritis drug Humira(TM); and

     o    other companies, including Medarex, Inc., are developing monoclonal
          antibody or other products for treatment of inflammatory skin
          disorders.

     A number of companies are developing monoclonal antibodies targeting
cancers, which may prove more effective than ONYX-015 or the ING-1 antibody.

     It is possible that one or more other companies may be developing one or
more products based on the same human protein as our NEUPREX(R) product, and
these product(s) may prove to be more effective than NEUPREX(R) or receive
regulatory approval prior to NEUPREX(R) or any BPI-derived ophthalmic product
developed by us.

As We Do More Business Internationally, We Will Be Subject To
Additional Political, Economic and Regulatory Uncertainties

     We may not be able to successfully operate in any foreign market. We
believe that, because the pharmaceutical industry is global in nature,
international activities will be a significant part of our future business
activities and that, when and if we are able to generate income, a substantial
portion of that income will be derived from product sales and other activities
outside the United States. Foreign regulatory agencies often establish standards
different from those in the United States, and an inability to obtain foreign
regulatory approvals on a timely basis could put us at a competitive
disadvantage or make it uneconomical to proceed with a product's development.
International operations may be limited or disrupted by:

     o    imposition of government controls

     o    export license requirements

     o    political or economic instability

     o    trade restrictions

     o    changes in tariffs



                                      -12-


     o    restrictions on repatriating profits

     o    exchange rate fluctuations

     o    withholding and other taxation and

     o    difficulties in staffing and managing international operations.

Because We Are A Relatively Small Biopharmaceutical Company With Limited
Resources, We May Not Be Able To Attract And Retain Qualified Personnel, And The
Loss Of Key Personnel Could Delay Or Prevent Achieving Our Objectives

     Our success in developing marketable products and achieving a competitive
position will depend, in part, on our ability to attract and retain qualified
scientific and management personnel, particularly in areas requiring specific
technical, scientific or medical expertise. There is intense competition for
such personnel. Our research, product development and business efforts would be
adversely affected by the loss of one or more of key members of our scientific
or management staff, particularly our executive officers: John L. Castello, our
Chairman of the Board, President and Chief Executive Officer; Patrick J.
Scannon, M.D., Ph.D., our Senior Vice President and Chief Scientific and Medical
Officer; Clarence L. Dellio, our Senior Vice President and Chief Operating
Officer; Peter B. Davis, our Vice President, Finance and Chief Financial
Officer; and Christopher J. Margolin, our Vice President, General Counsel and
Secretary. We have employment agreements with Mr. Castello, Dr. Scannon and Mr.
Davis. We currently have no key person insurance on any of our employees.

Even If We Bring Products To Market, We May Be Unable To Effectively Price Our
Products Or Obtain Adequate Reimbursement For Sales Of Our Products, Which Would
Prevent Our Products From Becoming Profitable.

     If we succeed in bringing our product candidates to the market, they may
not be considered cost-effective, and reimbursement to the patient may not be
available or may not be sufficient to allow us to sell our products on a
competitive basis. In both the United States and elsewhere, sales of medical
products and treatments are dependent, in part, on the availability of
reimbursement to the patient from third-party payors, such as government and
private insurance plans. Third-party payors are increasingly challenging the
prices charged for pharmaceutical products and services. Our business is
affected by the efforts of government and third-party payors to contain or
reduce the cost of health care through various means. In the United States,
there have been and will continue to be a number of federal and state proposals
to implement government controls on pricing. In addition, the emphasis on
managed care in the United States has increased and will continue to increase
the pressure on the pricing of pharmaceutical products. We cannot predict
whether any legislative or regulatory proposals will be adopted or the effect
these proposals or managed care efforts may have on our business.

Because We Engage In Human Testing, We Are Exposed
To An Increased Risk Of Product Liability Claims

     The testing and marketing of medical products entails an inherent risk of
allegations of product liability. We believe that we currently have adequate
levels of insurance for our clinical trials; however, in the event of one or
more large, unforeseen awards, such levels may not provide adequate coverage. We
will seek to obtain additional insurance, if needed, if and when our products
are commercialized; however, because we do not know when this will occur, we do
not know whether adequate insurance coverage will be available or be available
at acceptable costs. A significant product liability claim for which we were not
covered by insurance would have to be paid from cash or other assets. To the
extent we have sufficient insurance coverage, such a claim would result in
higher subsequent insurance rates.



                                      -13-


We May Be Subject To Increased Risks Because
We Are A Bermuda Company

     Alleged abuses by certain companies that have changed their legal domicile
from jurisdictions within the United States to Bermuda have created an
environment where, notwithstanding that we changed our legal domicile in a
transaction that was approved by our shareholders and fully taxable to our
company under U.S. law, we may be exposed to various prejudicial actions,
including:

     o    "blacklisting" of our common shares by certain pension funds

     o    legislation restricting certain types of transactions and

     o    punitive tax legislation.

     We do not know whether any of these things will happen, but if implemented
one or more of them may have an adverse impact on our future operations or our
share price.

If You Were To Obtain A Judgment Against Us, It May Be Difficult
To Enforce Against Us Because We Are A Foreign Entity

     We are a Bermuda company. All or a substantial portion of our assets may be
located outside the United States. As a result, it may be difficult for
shareholders and others to enforce in United States courts judgments obtained
against us. We have irrevocably agreed that we may be served with process with
respect to actions based on offers and sales of securities made hereby in the
United States by serving Christopher J. Margolin, c/o XOMA Ltd., 2910 Seventh
Street, Berkeley, California 94710, our United States agent appointed for that
purpose. We have been advised by our Bermuda counsel, Conyers Dill & Pearman,
that there is doubt as to whether Bermuda courts would enforce judgments of
United States courts obtained in (1) actions against us or our directors and
officers that are predicated upon the civil liability provisions of the U.S.
securities laws or (2) original actions brought in Bermuda against us or such
persons predicated upon the U.S. securities laws. There is no treaty in effect
between the United States and Bermuda providing for such enforcement, and there
are grounds upon which Bermuda courts may not enforce judgments of United States
courts. Certain remedies available under the United States federal securities
laws may not be allowed in Bermuda courts as contrary to that nation's policy.

Our Shareholder Rights Agreement Or Bye-laws May Prevent Transactions That Could
Be Beneficial To Our Shareholders And May Insulate Our Management From Removal

     In February of 2003, we renewed our shareholder rights agreement which
could make it considerably more difficult or costly for a person or group to
acquire control of XOMA in a transaction that our board of directors opposes.

     Our bye-laws:

     o    require certain procedures to be followed and time periods to be met
          for any shareholder to propose matters to be considered at annual
          meetings of shareholders, including nominating directors for election
          at those meetings;

     o    authorize our board of directors to issue up to 1,000,000 preference
          shares without shareholder approval and to set the rights, preferences
          and other designations, including voting rights, of those shares as
          the board of directors may determine; and



                                      -14-


     o    contain provisions, similar to those contained in the Delaware General
          Corporation Law, that may make business combinations with interested
          shareholders more difficult.

     These provisions of our shareholders rights agreement and our bye-laws,
alone or in combination with each other, may discourage transactions involving
actual or potential changes of control, including transactions that otherwise
could involve payment of a premium over prevailing market prices to holders of
common shares, could limit the ability of shareholders to approve transactions
that they may deem to be in their best interests and could make it considerably
more difficult for a potential acquiror to replace management.

Risks Relating To This Offering

The Actual Or Anticipated Resale By Millennium Of Our Common Shares That It
Purchases From Us Under The Investment Agreement Or Otherwise Owns Or Acquires
May Have An Adverse Impact On The Market Price Of Our Common Shares

     The resale by Millennium through open market transactions or other means of
the common shares that it purchases from us under the investment agreement, that
we issue to Millennium upon conversion of the convertible note we have issued to
them or that it otherwise owns or acquires may, depending upon the timing of the
resales, depress the market price of our common shares. Moreover, as all the
common shares we sell to Millennium or issue upon conversion will be available
for immediate resale, the mere prospect of our sales to it could depress the
market price of our common shares. In addition, actual or anticipated downward
pressure on the market price of our common shares due to actual or anticipated
resales of our common shares by Millennium could cause some institutions or
individuals to engage in short sales of our common shares, which may itself
cause the market price of our common shares to decline.

Our Issuance Of Common Shares To Millennium Will Reduce The Percentage Equity
Ownership Of Our Existing Shareholders

     Under our investment agreement with Millennium, we may issue to Millennium
up to $42.5 million worth of our common shares over the following 21 months on
several predetermined closing dates. The precise number of common shares that we
will issue to Millennium over the term of the investment agreement will depend
on the market price of our common shares during the period immediately preceding
the applicable closing date. Each issuance of common shares to Millennium
pursuant to the investment agreement will proportionately decrease our existing
shareholders' percentage ownership of our total outstanding equity interests.




                                      -15-




                INCORPORATION OF INFORMATION WE FILE WITH THE SEC

     The following documents filed by XOMA with the SEC pursuant to the
Securities Exchange Act are "incorporated by reference" in this prospectus,
which means we can disclose important information to you by referring you to
these documents and they are considered to be a part of this prospectus:

          (1) annual report on Form 10-K for the fiscal year ended December 31,
     2002 (file no. 0-14710);

          (2) quarterly report on Form 10-Q for the quarterly period ended March
     31, 2003 (file no. 0-14710);

          (3) current report on Form 8-K dated and filed on November 27, 2001,
     as amended by amendments on Form 8-K/A dated and filed on December 13,
     2001, October 24, 2002 and May 21, 2003, respectively (file no. 0-14710);
     and

          (4) the description of the common shares in the registration statement
     on Form 8-A dated and filed on May 21, 1999 under Section 12 of the
     Securities Exchange Act, including any amendment or report for the purpose
     of updating such description (registration no. 333-68045).

     All documents filed by XOMA with the SEC pursuant to Section 13(a), 13(c),
14 or 15(d) of the Securities Exchange Act after the date of this prospectus and
before all of the common shares offered by this prospectus have been sold are
deemed to be incorporated by reference in, and to be part of, this prospectus
from the date any such document is filed.

     Any statements contained in a document incorporated by reference in this
prospectus are deemed to be modified or superseded for purposes of this
prospectus to the extent that a statement contained in this prospectus (or in
any other subsequently filed document which also is incorporated by reference in
this prospectus) modifies or supersedes such statement. Any statement so
modified or superseded is not deemed to constitute a part of this prospectus
except as so modified or superseded.




                                      -16-




                SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

     Some of the statements made in this prospectus are forward-looking in
nature, including those relating to the relative size of the Company's loss for
2002, the estimated levels of its expenses and revenues for the balance of 2003,
the sufficiency of its cash resources, existing and potential collaborative and
licensing relationships and current plans for product development including the
progress of clinical trials and the regulatory process, as well as timing of
clinical trials and regulatory filings and approvals, or that otherwise relate
to future periods and other statements that are not historical facts. The words
"believe," "plan," "intend," "expect" and similar expressions are intended to
identify forward-looking statements. We caution you not to place undue reliance
on these forward-looking statements. They apply only as of the date of this
prospectus except that statements incorporated by reference from previously
filed reports apply as of the date made. The occurrence of the events described,
and the achievement of the intended results, depend on many events, some or all
of which are not predictable or not within our control. Actual results may
differ materially from those anticipated in any forward-looking statements. Many
risks and uncertainties are inherent in the biopharmaceutical industry. Others
are more specific to our business. Many of the significant risks related to our
business are described in this prospectus. These include, among others, the
actual loss for 2003 could be higher depending on revenues from licensees and
collaborators, the size and timing of expenditures and whether there are
unanticipated expenditures; the sufficiency of cash resources could be shortened
if expenditures are made earlier or in larger amounts than anticipated or are
unanticipated or if funds are not available; and regulatory approvals could be
delayed or denied as a result of safety or efficacy issues regarding the
products being tested, action, inaction or delay by the FDA, European or other
regulators, or issues relating to analysis, interpretation or submission of
scientific data. These and other risks, including those related to changes in
the status of the existing collaborative relationships, availability of
additional licensing or collaboration opportunities, the timing or results of
pending and future clinical trials, the ability of collaborators and other
partners to meet their obligations, market demand for products, actions by the
Food and Drug Administration or the U.S. Patent and Trademark Office, scale-up
and marketing capabilities, competition, international operations, share price
volatility, the Company's financing needs and opportunities, uncertainties
regarding the status of biotechnology patents, uncertainties as to the costs of
protecting intellectual property and risks associated with our status as a
Bermuda company are described in more detail in "Risk Factors." We undertake no
obligation to publicly update any forward-looking statements, regardless of any
new information, future events or other occurrences. We advise you, however, to
consult any additional disclosures we make in our reports to the SEC on Forms
10-K, 10-Q and 8-K.

                              ____________________

     We have not authorized any dealer, salesperson or other person to give you
written information other than this prospectus or to make representations as to
matters not stated in this prospectus. You must not rely on unauthorized
information. This prospectus is not an offer to sell these common shares or our
solicitation of your offer to buy the common shares in any jurisdiction where
that would not be permitted or legal. Neither the delivery of this prospectus
nor any sales made hereunder after the date of this prospectus should imply that
the information contained in this prospectus or the affairs of XOMA have not
changed since the date of this prospectus.




                                      -17-




              PRICE RANGE OF COMMON SHARES AND DIVIDEND INFORMATION

     XOMA's common shares (such common shares and the common stock of our
predecessor Delaware corporation are referred to in this prospectus as the
common shares) trade on the Nasdaq National Market under the symbol "XOMA." The
following table sets forth the quarterly range of high and low reported sale
prices of the common shares on the Nasdaq National Market for the periods
indicated (in United States dollars):

                                                         High          Low
                                                         ----          ---

    2001:
                 First Quarter                        $13.875         $6.031
                 Second Quarter                        17.750          5.313
                 Third Quarter                         17.090          6.740
                 Fourth Quarter                        10.500          6.400

    2002:

                 First Quarter                        $12.190         $7.510
                 Second Quarter                         8.510          3.000
                 Third Quarter                          7.200          3.250
                 Fourth Quarter                         6.250          3.800

    2003:

                 First Quarter                         $4.600         $2.840
                 Second Quarter (through May 20)       $8.000         $3.790

     On May 20, 2003 the last reported sale price of the common shares as
reported on the Nasdaq National Market was $5.98 per share. As of May 20, 2003,
there were approximately 3,160 record holders of XOMA's common shares.

     XOMA has not paid dividends on its common equity. XOMA currently does not
intend to pay dividends and intends to retain any earnings for use in its
business and the financing of its capital requirements for the foreseeable
future. The payment of any future cash dividends on XOMA's common shares will
necessarily be dependent upon the earnings and financial needs of XOMA, along
with applicable legal and contractual restrictions.




                                      -18-




                                 USE OF PROCEEDS

     We have used and intend to continue to use most of the net proceeds from
our sale of the common shares to the selling shareholders under the investment
agreement for the development of two of Millennium's biotherapeutic agents for
certain vascular inflammation indications pursuant to our collaboration
agreement with Millennium. Otherwise, we intend to use the net proceeds for
general corporate purposes, including current research and development projects,
the development of new products or technologies, equipment acquisitions, general
working capital and operating expenses.

     We have not determined the amounts we plan to spend on any of the areas
listed above or the timing of these expenditures. As a result, our management
will have broad discretion to allocate the net proceeds from our sale of the
common shares to the selling shareholders. Pending application of the net
proceeds as described above, we intend to invest the net proceeds in short-term,
investment-grade, interest-bearing securities.

     We will not receive any proceeds from the sale of the common shares by the
selling shareholders to you. To the extent shares are issued upon conversion of
the convertible note, we will benefit from the resulting cancellation of
indebtedness. The $5.0 million convertible subordinated note is convertible at
our option into our common shares.




                                      -19-




                              SELLING SHAREHOLDERS

     The selling shareholders are Millennium Pharmaceuticals, Inc. and its
wholly-owned subsidiary, mHoldings Trust, a Massachusetts business trust. On
November 26, 2001, Millennium and XOMA announced an agreement in which they will
collaborate to develop two of Millennium's biotherapeutic agents for certain
vascular inflammation indications. As previously announced, under an investment
agreement, Millennium has committed to purchase, at our option and subject to
certain conditions under the investment agreement, up to $50.0 million worth of
our common shares over the 30 months following the effective date of the
investment agreement on several predetermined closing dates, through a
combination of convertible debt and equity. On December 18, 2002, Millenium
purchased approximately 1.4 million of our common shares for $7.5 million to
satisfy, in part, its obligation under the investment agreement. On May 16,
2003, we and Millennium agreed to delay the maturity of the $5.0 million
convertible subordinated note until February 26, 2004 and to adjust the timing
of Millenium's obligation to purchase the remaining $37.5 million worth of our
common shares. At six subsequent closings over the following 21 months, we may
issue up to $4.0 million, $9.0 million, $7.0 million, $6.0 million, $6.0 million
and $5.5 million worth of our common shares, respectively.

     The following table sets forth certain information regarding the ownership
of common shares by the selling shareholders as of May 20, 2003, and the number
of common shares covered by this prospectus:




                                                                                                 Ownership
                                            Ownership                                         of common shares
                                         of common shares                             after the offering (assuming all
                                      prior to the offering                             shares offered are sold)(1)
                                     -----------------------                        -----------------------------------
                                                                    Number
              Name of                         Number               of Shares           Number of            Percent
        Selling Shareholders                of Shares               Offered             Shares              of Class
----------------------------------        -------------          ------------          ---------           ----------
                                                                                                  
Millennium Pharmaceuticals, Inc.          6,000,000(3)           6,000,000(4)               0                 0%
and its wholly-owned subsidiary,
mHoldings Trust(2)




(1)  For the purposes of this filing, we have assumed that all of the shares
     included in this registration statement will be sold; however, there is no
     contractual or other arrangement requiring any of the shares to be sold.

(2)  The management of Millennium has voting and investment control over the
     common shares.

(3)  Includes shares issuable upon conversion of the entire amount of principal
     outstanding ($5.0 million), plus accrued interest, under a convertible
     subordinated note held by Millennium and convertible at XOMA's option. Also
     includes 1,443,418 common shares issued to the selling shareholders on
     December 18, 2002 and common shares issuable to the selling shareholders,
     at our option and subject to certain conditions under the investment
     agreement, that we are registering for resale by the selling shareholders
     under this registration statement. We are registering 6,000,000 common
     shares based in part on our good faith estimate of the maximum number of
     common shares we have issued or may issue to Millennium under the
     investment agreement and upon conversion of the convertible debt.

(4)  Consists of shares issuable directly to Millennium by XOMA either for cash
     pursuant to the investment agreement between the parties or upon conversion
     at maturity of or upon an event of default under the $5.0 million
     convertible subordinated note of XOMA held by Millennium.



                                      -20-


     We are registering 6,000,000 common shares based in part on our good faith
estimate of the maximum number of common shares we have issued or may issue to
Millennium under the investment agreement and upon conversion of the convertible
debt. If the price of our common shares increases sufficiently, the number of
common shares we are registering for issuance may be higher than the number of
common shares we actually issue to Millennium under the investment agreement. In
such case, the number of shares resold by Millennium under this prospectus would
be less than the number of shares registered for resale. On the other hand, if
the price of our common shares decreases and the number of common shares we
actually issue to Millennium under the investment agreement is greater than the
number of shares we are now registering, we may need to file a new registration
statement with the Securities and Exchange Commission, which will need to become
effective prior to our completing the sales contemplated by the investment
agreement. The 6,000,000 common shares that we are registering consist of shares
issued or to be issued directly to Millennium by XOMA either for cash pursuant
to the investment agreement between the parties or upon conversion at maturity
of or upon an event of default under the $5.0 million convertible subordinated
note of XOMA held by Millennium.

     As of May 20, 2003, the selling shareholders hold 1,443,418 of our common
shares. Other than their obligation to purchase common shares at subsequent
closing dates under the investment agreement (at our option) and upon conversion
of the $5.0 million convertible note (at our option), the selling shareholders
have no commitments or arrangements to purchase any of our common shares.
Notwithstanding that the conversion by the selling shareholders of the $5.0
million convertible note is at our option, the selling shareholders may be
deemed to be beneficial owners of the approximately 0.84 million common shares
issuable upon the conversion of the convertible note as if the convertible note
had been converted on May 20, 2003. Assuming the selling shareholders sell all
of the common shares that they have acquired or may acquire under the investment
agreement and do not otherwise acquire our common shares, they will not own any
of our common shares after their sale of the common shares to you.

Material Terms Of Investment Agreement

     On November 26, 2001, Millennium and XOMA entered into an investment
agreement which committed Millennium to purchase, at our option and subject to
the conditions described in the following paragraph, up to $50.0 million worth
of our common shares over the 30 months following the effective date of the
investment agreement. Of the up to $50.0 million worth of our common shares,
$5.0 million worth (and accrued interest) may be issued at our option upon
conversion of a convertible subordinated note already issued to Millennium, the
entire principal amount of which is currently outstanding. On December 18, 2002,
Millenium purchased approximately 1.4 million of our common shares for $7.5
million to satisfy, in part, its obligation under the investment agreement. On
May 16, 2003, we and Millennium agreed to delay the maturity of the $5.0 million
convertible subordinated note until February 26, 2004 and to adjust to timing of
Millenium's obligation to purchase the remaining $37.5 million worth of our
common shares. At six subsequent closings over the following 21 months, we may
issue up to $4.0 million, $9.0 million, $7.0 million, $6.0 million, $6.0 million
and $5.5 million worth of our common shares, respectively. At each closing, the
precise number of shares to be purchased by Millennium will be determined using
a formula based on the average of certain sale prices per common share as
reported on the Nasdaq National Market for a specified period of time prior to
the applicable closing date (subject to certain adjustments and limitations).
The formula is intended to reflect the current market price per common share at
the time of each closing, without any discount or premium.

     The obligations of Millennium to purchase the common shares that we wish to
sell at each closing will be subject to customary closing conditions, including
the delivery of legal opinions and certificates of our officers and updated
financial information, the continued listing of our common shares on the Nasdaq
National Market or the New York or American Stock Exchanges, the continued
effectiveness of the registration statement that includes this prospectus and
the continuation of our collaboration agreement with Millennium.

     We have agreed to register the resale of the common shares that we may sell
to Millennium at each closing and the common shares that we may issue to
Millennium upon conversion of the convertible debt. The registration statement
that includes this prospectus is intended to satisfy these registration
obligations. We will



                                      -21-


consummate the first direct sale of common shares to Millennium after the
registration statement that includes this prospectus is declared effective.

     The 6,000,000 shares registered under the registration statement that
includes this prospectus would have represented 7.8% of our outstanding common
shares as of May 20, 2003, after giving effect to their issuance. Based on the
current market price of our common shares, the investment agreement gives us the
option to require the selling shareholders to purchase an aggregate of up to
approximately 7.1 million common shares (assuming conversion of the convertible
subordinated note) for $42.5 million, in addition to the 1.4 million common
shares already purchased.

Conversion Provisions Of Convertible Subordinated Note

     The principal and accrued interest on the convertible subordinated note may
be converted in whole (but not in part) at our election upon maturity into our
common shares. The number of shares into which the convertible subordinated note
may be converted will be determined using a formula based on the average of
certain sale prices per common share as reported on the Nasdaq National Market
for a specified period of time prior to the conversion date (subject to certain
adjustments and limitations). The formula is intended to reflect the current
market price per common share at the time of conversion, without any discount or
premium. Based on the current market price of our common shares, we would be
entitled to issue an aggregate of approximately 0.84 million common shares in
full payment of the convertible subordinated note.

     If we do not elect to convert the convertible subordinated note into common
shares, all outstanding principal and all accrued interest must be paid to
Millennium in cash on the maturity date, unless otherwise agreed.

     In addition to customary restrictions on our ability to convert, we will
not be entitled to convert any portion of the convertible subordinated note or
the accrued interest unless there is on the conversion date an effective
registration statement covering resale of all of the common shares into which
the principal of the convertible note and all accrued interest would convert. If
this is not the case at any time prior to its maturity date, then the
convertible subordinated note will remain outstanding until its maturity date
and, if no such effective registration statement is then in place, we will be
required to repay all outstanding principal and accrued interest in cash on the
maturity date. The registration statement that includes this prospectus is
intended to satisfy these registration obligations.




                                      -22-




                          DESCRIPTION OF SHARE CAPITAL

     The following statements with respect to our share capital are subject to
the detailed provisions of our memorandum of continuance and bye-laws. These
statements do not purport to be complete and, while we believe the descriptions
of the material provisions of the memorandum of continuance and bye-laws
incorporated by reference are accurate statements with respect to such material
provisions, such statements are subject to the detailed provisions in the
memorandum of continuance and bye-laws, to which reference is hereby made for a
full description of such provisions.

COMMON SHARES

General

     The memorandum of continuance and the bye-laws provide that our authorized
common share capital is limited to 135,000,000 common shares, par value
U.S.$.0005 per share. As of May 20, 2003, there were 71,999,924 common shares
outstanding.

Voting

     The holders of common shares are entitled to one vote per share. All
actions submitted to a vote of shareholders shall be voted on by the holders of
common shares, voting together as a single class (together with the Series A
preference shares (as described below), if any), except as provided by law.

Dividends

     Holders of common shares are entitled to participate, on a share for share
basis, with the holders of any other common shares outstanding, with respect to
any dividends declared by our board of directors, subject to the rights of
holders of preference shares. Dividends will generally be payable in U.S.
dollars. We have not paid cash dividends on the common shares. We currently do
not intend to pay dividends and intend to retain any of our earnings for use in
our business and the financing of our capital requirements for the foreseeable
future. The payment of any future cash dividends on the common shares is
necessarily dependent upon our earnings and financial needs, along with
applicable legal and contractual restrictions.

Liquidation

     On a liquidation of XOMA, holders of common shares will be entitled to
receive any assets remaining after the payment of our debts and the expenses of
the liquidation, subject to such special rights as may be attached to any other
class of shares.

Redemption

     The common shares are not subject to redemption either by us or the holders
thereof.

Variation of Rights

     Under our bye-laws, if at any time our share capital is divided into
different classes of shares, the rights attached to any class (unless otherwise
provided by the terms of the issue of the shares of that class) may be varied
with the consent in writing of the holders of a majority of the issued shares of
that class either in writing or with the sanction of a resolution passed at a
separate general meeting.



                                      -23-


PREFERENCE SHARES

General

     Under our memorandum of continuance and bye-laws, we have the authority to
issue 1,000,000 preference shares, par value U.S.$.05 per share. Of these,
135,000 preference shares have been designated Series A Preference Shares and
8,000 preference shares have been designated Series B Preference Shares. Under
our bye-laws, subject to the special rights attaching to any class of our shares
not being varied and to any resolution approved by the holders of 75% of the
issued shares entitled to vote in respect thereof, our board of directors may
establish one or more classes or series of preference shares having the number
of shares, designations, relative voting rights, dividend rates, liquidation and
other rights, preferences and limitations that the board of directors fixes
without any shareholder approval.

The Series A Preference Shares

     There are no Series A preference shares outstanding. Pursuant to the rights
of the Series A preference shares, subject to the rights of holders of any
shares of any series of preference shares ranking prior and superior, the
holders of Series A preference shares are entitled to receive, when, as and if
declared by our board of directors out of funds legally available for the
purpose, quarterly dividends payable in cash on the first day of March, June,
September and December in each year, commencing on the first dividend payment
date after the first issuance of a share or fraction of a share of Series A
preference shares, in an amount per share equal to the greater of (a) U.S.$1.00
or (b) 1,000 times the aggregate per share amount of all cash dividends, plus
1,000 times the aggregate per share amount of all non-cash dividends or other
distributions, other than a dividend or bonus issue payable in common shares,
declared on the common shares since the immediately preceding dividend payment
date, or, with respect to the first dividend payment date, since the first
issuance of Series A preference shares.

     In addition to any other voting rights required by law, holders of Series A
preference shares shall have the right to vote on all matters submitted to a
vote of our shareholders with each share of Series A preference shares entitled
to 1,000 votes. Except as otherwise provided by law, holders of Series A
preference shares, holders of common shares and holders of any other shares
having general voting rights shall vote together as one class on all matters
submitted to a vote of our shareholders.

     Unless otherwise provided in the rights attaching to a subsequently
designated series of our preference shares, the Series A preference shares shall
rank junior to any other series of preference shares subsequently issued as to
the payment of dividends and distribution of assets on liquidation, dissolution
or winding-up and shall rank senior to the common shares. Upon any liquidation,
dissolution or winding-up of XOMA, no distributions shall be made to holders of
shares ranking junior to the Series A preference shares unless, prior thereto,
the holders of Series A preference shares shall have received an amount equal to
accrued and unpaid dividends and distributions, whether or not declared, to the
date of such payment, plus an amount equal to the greater of (1) U.S.$100.00 per
share or (2) an aggregate amount per share equal to 1,000 times the aggregate
amount to be distributed per share to holders of common shares or to the holders
of shares ranking on parity with the Series A preference shares, except
distributions made ratably on the Series A preference shares and all other such
parity shares in proportion to the total amount to which the holders of all such
shares are entitled upon such liquidation, dissolution or winding-up.

     If we shall enter into any consolidation, amalgamation, merger, combination
or other transaction in which common shares are exchanged for or changed into
cash, other securities and/or any other property, then any Series A preference
shares outstanding shall at the same time be similarly exchanged or changed in
an amount per share equal to 1,000 times the aggregate amount of cash,
securities and/or other property, as the case may be, into which or for which
each common share is changed or exchanged.

     The Series A preference shares shall not be redeemable.



                                      -24-


The Series B Preference Shares

     There are no Series B preference shares outstanding. The 8,000 Series B
preference shares have been designated for issuance upon conversion of the
convertible subordinated loans to us made and to be made by Genentech in
connection with the funding of the our development costs for Raptiva(TM). Such
loans are and will be convertible into Series B preference shares upon the
occurrence of certain events relating to certain regulatory approvals, payment
defaults, prepayments and other circumstances. Pursuant to the rights of the
Series B preference shares, the holders of Series B preference shares will not
be entitled to receive any dividends on the Series B preference shares.

     The Series B preference shares will rank senior with respect to rights on
liquidation, winding-up and dissolution of XOMA to all classes of common shares.
Upon any voluntary or involuntary liquidation, dissolution or winding-up of
XOMA, holders of Series B preference shares will be entitled to receive
U.S.$10,000 per share of Series B preference shares before any distribution is
made on the common shares. The holders of Series B preference shares will have
no voting rights, except as required under Bermuda law.

     The holders of Series B preference shares will have the right to convert
Series B preference shares into common shares at a conversion price equal to the
current market price of the common shares (determined as provided below). The
current market price will be determined (a) for Series B preference shares
issued in connection with a conversion of one or more of the convertible
subordinated loans upon certain regulatory approvals, payment defaults or in
certain other circumstances, as of the first date on which such a conversion
occurs, and (b) for Series B preference shares issued in connection with certain
prepayments of one or more of the convertible subordinated loans or a conversion
thereof in certain other circumstances, as of the date of the issuance of such
Series B preference shares.

     The Series B preference shares will be automatically converted into common
shares at its then effective conversion rate immediately upon the transfer by
the initial holder to any third party which is not an affiliate of such holder.

     We will have the right, at any time and from time to time, to redeem any or
all Series B preference shares for cash in an amount equal to the conversion
price multiplied by the number of common shares into which each such share of
Series B preference shares would then be convertible.

OUTSTANDING WARRANTS

     XOMA issued 250,000 common stock purchase warrants to Incyte in July of
1998, of which 125,000 remain outstanding. Each Incyte warrant outstanding
entitles the holder thereof to purchase one common share, subject to
anti-dilution adjustments. A holder may exercise the Incyte warrants at an
exercise price of $6.00 per share on or before July 9, 2008 or earlier upon the
related license becoming fully paid up. Incyte is the holder of these warrants
and received them as part of the consideration for the grant to XOMA of an
exclusive license to all of Incyte's patent rights relating to BPI.

     XOMA issued 379,000 warrants to purchase common shares in January of 1999
and March of 1999, of which 175,000 remain outstanding. Each January and March
1999 warrant entitles the holder thereof to purchase one common share, subject
to anti-dilution adjustments. A holder may exercise the January and March 1999
warrants at an exercise price of $5.85 per share on or before January 29, 2004.
Advantage Fund II Ltd. and Koch Investment Group Limited are the holders of
these warrants and received them in connection with their purchase of our common
shares in a private placement in January of 1999.

     XOMA issued 150,000 warrants to purchase common shares in July of 1999.
Each July 1999 warrant entitles the holder thereof to purchase one common share,
subject to anti-dilution adjustments. A holder may exercise the July 1999
warrants at an exercise price of $5.75 per share on or before July 21, 2004.
Sutro & Co.



                                      -25-


Incorporated and Arnhold and S. Bleichroeder, Inc. are the holders of these
warrants and received them as consideration for their services as placement
agents for a private placement of our common shares in July of 1999.

     XOMA issued 250,000 warrants to purchase common shares in February of 2000.
Each February 2000 warrant entitles the holder thereof to purchase one common
share, subject to anti-dilution adjustments. A holder may exercise the February
2000 warrants at an exercise price of $5.00 per share on or before February 11,
2005. Sutro & Co. Incorporated and Arnhold and S. Bleichroeder, Inc. are the
holders of these warrants and received them as consideration for their services
as placement agents for a private placement of our common shares in February of
2000.

     All of the warrants described above were issued in reliance on the
exemption from registration provided in Section 4(2) of the Securities Act. None
of the warrants described above have been registered under the Securities Act
and none may be transferred except pursuant to an effective registration
statement under the Securities Act or pursuant to an exception from registration
thereunder. Additionally, all of the warrants contain certain restrictions on
their transfer. XOMA is not obligated and does not intend to register the
warrants under the Securities Act.

                              PLAN OF DISTRIBUTION

     Any or all of the common shares being offered by this prospectus may be
sold from time to time to purchasers directly by the selling shareholders or by
pledgees, donees, transferees or other successors in interest. Alternatively,
the selling shareholders may from time to time offer any or all of the common
shares through underwriters, brokers, dealers or agents who may receive
compensation in the form of underwriting discounts, concessions or commissions
from such selling shareholder and/or the purchasers of common shares for whom
they may act. The selling shareholders, and any such underwriters, brokers,
dealers or agents that participate in the distribution of common shares, are
underwriters, and any profit on the sale of the common shares by them and any
discounts, commissions or concessions received by them may be deemed to be
underwriting discounts and commissions under the Securities Act. Any such common
shares may be so offered or sold in the open market, on the Nasdaq National
Market or such other exchange or market where our common shares are then traded,
in privately negotiated transactions (subject to limitations imposed by the
investment agreement), in an underwritten offering, in block trades, to a broker
or dealer for its account in ordinary brokerage transactions, or a combination
of such methods. The selling shareholders will make such sales at market prices
prevailing at the time of sale, at prices related to such prevailing market
prices or at negotiated prices. To the extent required, the name of the selling
shareholder, the number of common shares to be sold, the purchase price, the
public offering price, the name of any agent, dealer, broker or underwriter and
any applicable commission or discount or other items constituting compensation
or indemnification arrangements with respect to a particular offering will be
set forth in an accompanying prospectus supplement. These and other matters may
also be addressed in one or more post-effective amendments to the registration
statement of which this prospectus is a part. XOMA will receive no proceeds from
the sale by the selling shareholders of the common shares offered by this
prospectus.

     In connection with distributions of the common shares, and subject to
limitations imposed by the investment agreement, the selling shareholders may
enter into option or other transactions with broker-dealers that involve the
delivery of the common shares to the broker-dealers, which may then resell or
otherwise transfer such common shares. The selling shareholder also may loan or
pledge the common shares to a broker-dealer and the broker-dealer may sell the
common shares so loaned or upon a default may sell or otherwise transfer the
pledged common shares.

     In addition, the selling shareholders and any other persons participating
in the sale or distribution of the shares offered by this prospectus will be
subject to liability under the federal securities laws and must comply with the
requirements of the Securities Act and the Securities Exchange Act, including
Rule 10b-5 and Regulation M under the Securities Exchange Act. These rules and
regulations may limit the timing of purchases and sales of our common shares by
the selling shareholders or such other persons. Under these rules and
regulations, the selling shareholders and such other persons:



                                      -26-


     o    may not engage in any stabilization activity in connection with our
          common shares;

     o    must furnish each broker which offers our common shares covered by
          this prospectus with the number of copies of this prospectus and any
          prospectus supplement which are required by such broker; and

     o    may not bid for or purchase any of our common shares or attempt to
          induce any person to purchase any of our common shares other than as
          permitted under the Securities Exchange Act.

     These restrictions may affect the marketability of our common shares by the
selling shareholders.

     The selling shareholders have agreed, subject to certain conditions, to a
restriction on their sales in the public market based on the trading volume of
our common shares and that they will not sell shares other than in the public
market without our prior written consent.

     To permit the selling shareholders to resell our common shares purchased by
it under the investment agreement, we agreed to register those shares and to
maintain that registration. We have also agreed with the selling shareholders
that, subject to limited exceptions for specified time periods, we will prepare
and file any amendments and supplements to this prospectus and the registration
statement of which it is a part as may be necessary to keep the registration
statement current and effective until:

     o    the date on which the selling shareholders may sell all of the common
          shares then held by the selling shareholders that they purchased from
          us under the investment agreement without restriction by the volume
          limitations of Rule 144(e) of the Securities Act; or

     o    the date after which all of our common shares held by the selling
          shareholders that are covered by the registration statement have been
          sold by the selling shareholders under a registration statement or
          pursuant to Rule 144.

     We have agree to indemnify and hold harmless the selling shareholders, any
broker-dealer named in the registration statement of which this prospectus is a
part and their respective controlling persons against certain liabilities,
including liabilities under the Securities Act, which may be based upon, among
other things, any untrue statement or alleged untrue statement of a material
fact contained in or incorporated by reference into the registration statement
or any omission or alleged omission to state in the registration statement or
any document incorporated by reference into the registration statement a
material fact required to be stated therein or necessary to make the statements
therein not misleading, unless made or omitted in reliance upon and in
conformity with written information provided to us by the selling shareholders
or such broker-dealer.

     All expenses incurred by XOMA in complying with the registration rights
granted to the selling shareholder pursuant to which the registration statement
to which this prospectus relates has been filed, estimated to be approximately
$117,000, will be borne by XOMA. As and when XOMA is required to update this
prospectus, it may incur additional expenses in excess of this estimated amount.

     Any common shares offered by this prospectus that qualify for sale pursuant
to Rule 144 under the Securities Act may be sold under such rule rather than
pursuant to this prospectus.

                                  LEGAL OPINION

     The validity of the common shares to which this prospectus relates has been
passed upon for XOMA by Conyers Dill & Pearman, located in Hamilton, Bermuda.



                                      -27-


                                     EXPERTS

     The consolidated financial statements of XOMA Ltd. appearing in XOMA Ltd.'s
Annual Report (Form 10-K) for the year ended December 31, 2002, have been
audited by Ernst & Young LLP, independent auditors, as set forth in their report
thereon included therein and incorporated herein by reference. Such consolidated
financial statements are incorporated herein by reference in reliance upon such
report given on the authority of such firm as experts in accounting and
auditing.

                       WHERE YOU CAN GET MORE INFORMATION

     This prospectus is part of a registration statement that we have filed with
the SEC. The registration statement contains exhibits and other information not
included in this prospectus. At your request, we will provide you, without
charge, a copy of any documents incorporated by reference in, or included as
exhibits to, our registration statement. If you would like more information,
write or call us at:

                                    XOMA Ltd.
                               2910 Seventh Street
                               Berkeley, CA 94710
                            Telephone: (510) 204-7273

     XOMA files annual, quarterly and current reports, proxy statements and
other information with the SEC. You may read and copy any reports, statements
and other information we file at the SEC's public reference room at 450 Fifth
Street, N.W., Washington D.C. 20549. You can request copies of these documents,
upon payment of a duplicating fee, by writing to the SEC. Please call the SEC at
1-800-SEC-0330 for further information on the operation of the public reference
room. XOMA's SEC filings are also available to the public on the SEC Internet
site at http://www.sec.gov.



                                      -28-