As filed with the Securities and Exchange Commission on April 17, 2006
                         Registration Statement No. 333-


                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                 ---------------

                                    FORM S-3

             REGISTRATION STATEMENT UNDERTHE SECURITIES ACT OF 1933
                                 ---------------

                          MISSION WEST PROPERTIES, INC.
             (Exact name of Registrant as specified in its charter)

           Maryland                                   95-2635431
(State or other jurisdiction of          (I.R.S. Employer Identification Number)
 incorporation or organization)

                               10050 Bandley Drive
                        Cupertino, California 95014-2102
                                 (408) 725-0700
    (Address, including zip code, and telephone number, including area code,
                  of Registrant's principal executive offices)

                                  Carl E. Berg
                      Chairman and Chief Executive Officer
                          Mission West Properties, Inc.
                               10050 Bandley Drive
                        Cupertino, California 95014-2102
                                 (408) 725-0700
    (Address, including zip code, and telephone number, including area code,
                          agent for service of process)
                                 ---------------

                        Copies of all communications to:

                                  Alan B. Kalin
                              Bingham McCutchen LLP
                             1900 University Avenue
                      East Palo Alto, California 94303-2223






     If the only  securities  being  registered  on this form are being  offered
pursuant to dividend or interest  reinvestment plans, please check the following
box. [ ]

     If any of the securities being registered on this Form are to be offered on
a delayed or continuous  basis  pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, please check the following box. [X]

     If this Form is filed to  register  additional  securities  for an offering
pursuant to Rule 462(b) under the  Securities  Act,  check the following box and
list the  Securities  Act  registration  statement  number of earlier  effective
registration statement for the same offering. [ ]

     If this Form is a  post-effective  amendment  filed pursuant to Rule 462(c)
under the  Securities  Act,  check the following box and list the Securities Act
registration  statement number of the earlier effective  registration  statement
for the same offering: [ ]

     If this Form is a registration  statement  pursuant to General  Instruction
I.D. or a  post-effective  amendment  thereto that shall become  effective  upon
filing with the  Commission  pursuant to Rule 462(e) under the  Securities  Act,
check the following box. [ ]

     If this Form is a  post-effective  amendment  to a  registration  statement
filed  pursuant  to  General  Instruction  I.D.  filed  to  register  additional
securities or additional classes of securities pursuant to Rule 413(b) under the
Securities Act, check the following box. [ ]



                         CALCULATION OF REGISTRATION FEE

---------------------------------------- ----------------- ---------------- ---------------------- -------------------
                                                              Proposed            Proposed
                                              Amount           Maximum             Maximum
                                              to be        Offering Price         Aggregate            Amount of
Title of Shares to Be Registered          Registered (1)    Per Share (2)    Offering Price (2)     Registration Fee
---------------------------------------- ----------------- ---------------- ---------------------- -------------------
                                                                                         
Common Stock, $.001 par value per share     86,088,095         $11.25          $968,491,068.75        $103,628.54
---------------------------------------- ----------------- ---------------- ---------------------- -------------------



(1)  In  addition to the common  stock set forth in the table,  the amount to be
     registered includes an indeterminate  number of shares issuable pursuant to
     stock splits and stock  dividends in accordance  with Rule 416(b) under the
     Securities Act of 1933, as amended.

(2)  Estimated solely for purposes of calculating the amount of the registration
     fee. The estimate is made pursuant to Rule 457(c) of the  Securities Act of
     1933,  as amended.  The price per share is based on the average of the high
     and low  prices  reported  on the  American  Stock  Exchange  for shares of
     Registrant's common stock on April 12, 2006.

     PURSUANT TO RULE 429 UNDER THE  SECURITIES  ACT OF 1933,  AS  AMENDED,  THE
PROSPECTUS INCLUDED IN THIS REGISTRATION  STATEMENT IS A COMBINED PROSPECTUS AND
RELATES TO  REGISTRATION  STATEMENT  NO.  333-52835-99  PREVIOUSLY  FILED BY THE
REGISTRANT AND DECLARED EFFECTIVE ON NOVEMBER 23, 1998. UPON EFFECTIVENESS, THIS
REGISTRATION  STATEMENT,  WHICH  IS A  NEW  REGISTRATION  STATEMENT,  WILL  ALSO
CONSTITUTE  A   POST-EFFECTIVE   AMENDMENT   TO   REGISTRATION   STATEMENT   NO.
333-52835-99.


--------------------------------------------------------------------------------
THE REGISTRANT HEREBY AMENDS THIS  REGISTRATION  STATEMENT ON SUCH DATE OR DATES
AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT  SHALL FILE
A FURTHER AMENDMENT WHICH SPECIFICALLY  STATES THAT THIS REGISTRATION  STATEMENT
SHALL  THEREAFTER  BECOME  EFFECTIVE  IN  ACCORDANCE  WITH  SECTION  8(A) OF THE
SECURITIES  ACT OF 1933,  OR  UNTIL  THE  REGISTRATION  STATEMENT  SHALL  BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION,  ACTING PURSUANT TO SAID SECTION 8(A),
MAY DETERMINE.
--------------------------------------------------------------------------------






The  information  in this  prospectus  is not complete  and may be changed.  The
securities  described in this prospectus may not be sold until the  registration
statement filed with the Securities and Exchange  Commission is effective.  This
prospectus is not an offer to sell these  securities and it is not soliciting an
offer  to buy  the  securities  in any  state  where  the  offer  or sale is not
permitted.

                             SUBJECT TO COMPLETION,
                              Dated: April 17, 2006

                                   PROSPECTUS
                        86,088,095 Shares of Common Stock
                                 $.001 par value

                          Mission West Properties, Inc.
                               10050 Bandley Drive
                        Cupertino, California 95014-2102
                                 (408) 725-0700


     This prospectus  relates to the public offering of up to 86,088,095  shares
of  common  stock  which  we may  issue  to the  holders  of  units  of  limited
partnership  interests,   or  O.P.  units,  in  our  four  controlled  operating
partnerships,  in exchange or redemption for an equal number of O.P. units under
the terms of existing agreements between us and these holders who we refer to as
the "selling  stockholders."  We will not receive any proceeds from any possible
sale of the common shares by the selling stockholders. For information regarding
the selling stockholders, see "Selling Stockholders" beginning on page 2 of this
prospectus.

     We are  registering  the  shares  of common  stock  being  offered  by this
prospectus  in order to permit the  selling  stockholders  to sell them  without
restriction, in the open market or otherwise.  However, the registration of such
shares does not  necessarily  mean that any of the O.P.  units will be submitted
for  exchange  or  redemption  or that any of the  shares of common  stock to be
issued in exchange or redemption  for the O.P.  units will be offered or sold by
the selling stockholders.

     The selling  stockholders  may offer their shares of common  stock  through
public or  private  transactions,  on or off the  United  States  exchanges,  at
prevailing market prices, or at privately  negotiated  prices.  This offering is
not being underwritten.

     The common stock is listed on the American  Stock  Exchange and the Pacific
Exchange and trades on these stock exchanges with the symbol "MSW". On April __,
2006 the closing price of one share of common  stock,  as quoted on the American
Stock Exchange was $____.

                                ----------------
  THE SHARES OF COMMON STOCK INVOLVE A HIGH DEGREE OF RISK. SEE "RISK FACTORS"
                              BEGINNING ON PAGE 1.
                                ----------------

     Neither the  Securities and Exchange  Commission  nor any state  securities
commission has approved or disapproved the shares of these  securities or passed
upon the  adequacy or accuracy of this  prospectus.  Any  representation  to the
contrary is a criminal offense.


                 The date of this prospectus is April __, 2006.







                                TABLE OF CONTENTS

                                                                                                      Page
                                                                                                   
Our Company......................................................................................      1
Risk Factors.....................................................................................      1
Use of Proceeds..................................................................................      2
The Selling Stockholders.........................................................................      2
Plan of Distribution.............................................................................      4
Where You Can Find More Information..............................................................      5
Incorporation by Reference.......................................................................      6
Legal Matters....................................................................................      6
Recent Developments..............................................................................      6
Experts..........................................................................................      7


     In this prospectus,  "Mission West," "we," "us," and "our" refer to Mission
West Properties, Inc.

     You should rely only on information  contained or incorporated by reference
in this  prospectus.  We have not  authorized  any  person to  provide  you with
information  that differs from what is contained or incorporated by reference in
this  prospectus.  If any person does provide you with  information that differs
from what is contained or  incorporated  by  reference in this  prospectus,  you
should  not  rely  on it.  This  prospectus  is  not an  offer  to  sell  or the
solicitation  of an offer to buy any  securities  other than the  securities  to
which it relates,  or an offer of solicitation in any jurisdiction  where offers
or sales are not  permitted.  The  information  contained in this  prospectus is
accurate only as of the date of this prospectus, even though this prospectus may
be delivered or shares may be sold under this prospectus on a later date.


                SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

     Some  of  the  statements  in  this  prospectus   contain   forward-looking
statements  within the meaning of the federal  securities  laws.  We intend such
forward-looking  statements  to be covered  by the safe  harbor  provisions  for
forward-looking statements contained in the Private Securities Litigation Reform
Act of 1995,  and are including  this  statement for purposes of complying  with
these safe harbor provisions.


     Forward-looking  statements,  which are based on  certain  assumptions  and
describe  future  plans,  strategies  and  expectations  of  us,  are  generally
identifiable by use of the words "believe,"  "expect,"  "intend,"  "anticipate,"
"estimate," "project" or similar expressions.

     Our  ability to predict  results  or the actual  effect of future  plans or
strategies is inherently uncertain.  Factors which could have a material adverse
effect on our operations and future prospects  include,  but are not limited to,
changes  in  economic   conditions   generally   and  the  real  estate   market
specifically,  legislative  or  regulatory  provisions  affecting us  (including
changes  to laws  governing  the  taxation  of  Real  Estate  Investment  Trusts
("REITs")),  availability of capital, interest rates, competition, supply of and
demand for office and industrial  properties in our current and proposed  market
areas,  tenant defaults and  bankruptcies,  and general  accounting  principles,
policies and  guidelines  applicable  to REITs.  These risks and  uncertainties,
together with the other risks  incorporated  by reference  under "Risk  Factors"
below or described from time to time in our reports and documents filed with the
Securities and Exchange  Commission (the "SEC" or the  "Commission"),  should be
considered in evaluating  forward-looking  statements, and undue reliance should
not be placed on such statements.

     Moreover,  neither we nor any other person assumes  responsibility  for the
accuracy and  completeness  of these  statements.  We undertake no obligation to
update or revise any of the forward-looking  statements,  whether as a result of
new information, future events or otherwise, except as required by law. In light
of these  risks,  uncertainties  and  assumptions,  the  forward-looking  events
discussed or incorporated by reference in this prospectus may not occur.

                                     - i -





                                   OUR COMPANY


     Mission  West  acquires,   markets,   leases,   and  manages  research  and
development  ("R&D") properties  primarily located in the Silicon Valley portion
of the San Francisco Bay Area. As of December 31, 2005, we owned and managed 107
properties totaling  approximately 7.8 million rentable square feet through four
limited  partnerships,  or  operating  partnerships,  for  which we are the sole
general  partner.  R&D property is designed for  research  and  development  and
office  uses  and,  in  some  cases,  includes  space  for  light  manufacturing
operations  with  loading  docks.  We  believe  that we have one of the  largest
portfolios  of R&D  properties  in the Silicon  Valley.  For federal  income tax
purposes  we  have  operated  as a  self-managed,  self-administered  and  fully
integrated REIT since fiscal 1999.

     In May 1998, Mission West, Carl E. Berg, his brother Clyde J. Berg, certain
members of their respective  immediate  families,  and certain entities in which
Carl E. Berg and/or Clyde J. Berg held controlling or other ownership  interests
(collectively  referred  to as the "Berg  Group")  and  certain  other  persons,
including John T. Kontrabecki,  entered into an acquisition  agreement to effect
an UPREIT transaction, which provided among other things, for our acquisition of
interests as the sole general partner in each of the four operating partnerships
named Mission West Properties,  L.P.,  Mission West Properties,  L.P. I, Mission
West Properties,  L.P. II, and Mission West Properties,  L.P. III. In July 1998,
the parties  amended the  acquisition  agreement  and agreed to  consummate  our
acquisition  of  the  general  partner   interests  in  each  of  the  operating
partnerships  effective for financial  and income tax  accounting  and reporting
purposes as of July 1, 1998.  At that time,  all  existing  limited  partnership
interests in the operating  partnerships  were reclassified into 59,479,633 O.P.
units which could be exchanged  for shares of our common  stock  pursuant to the
terms of an  exchange  rights  agreement.  Under  the  terms of the  acquisition
agreement, the operating partnerships and we also agreed to enter into a Pending
Projects Acquisition Agreement, which permitted the acquisition by the operating
partnerships of approximately 1.0 million  additional  rentable square feet upon
the completion and leasing of a number of the pending development projects owned
by certain members of the Berg Group. The acquisition  agreement also gave us an
option to  acquire,  through the  operating  partnerships,  future R&D  Property
developments on Silicon Valley land owned by members of the Berg Group under the
terms of the Berg Land  Holdings  Option  Agreement  and provided  that the Berg
Group members could elect to receive cash or O.P. units upon our exercise of the
option.  Since  July  1,  1998,  we  have  acquired  approximately  3.1  million
additional  rentable square feet of R&D properties from the Berg Group under the
Pending  Projects  Acquisition  Agreement  and the  Berg  Land  Holdings  Option
Agreement for a total cost of  approximately  $633.0  million.  We have issued a
total of 27,962,025  O.P. units and assumed debt totaling  approximately  $308.0
million to acquire these properties.

     Our  principal  executive  offices  are  located  at 10050  Bandley  Drive,
Cupertino, California 95014, and our telephone number is (408) 725-0700.


                                  RISK FACTORS

     An  investment  in our  common  stock is risky.  Prior to making a decision
about investing in our common stock, you should carefully  consider the specific
risks  discussed under Item 1A. "Risk Factors" in our Annual Report on Form 10-K
for the year ended December 31, 2005,  filed on March 16, 2006, and in our other
filings with the SEC, which are  incorporated  by reference in this  prospectus,
together with all of the other  information  contained in this  prospectus,  any
applicable prospectus supplement, or otherwise incorporated by reference in this
prospectus. The risks and uncertainties described in our SEC filings are not the
only ones facing us.  Additional risks and  uncertainties not presently known to
us, or that we currently see as immaterial,  may also harm our business.  If any
of the risks or uncertainties  described in the applicable prospectus supplement
or our SEC  filings  or any such  additional  risks and  uncertainties  actually
occur, our business,  results of operations,  cash flows and financial condition
could be materially and adversely  affected.  In that case, the trading price of
our  common  stock  could  decline,  and  you  might  lose  all or  part of your
investment.

                                     - 1 -


                                 USE OF PROCEEDS

     All net proceeds from the sale of the shares of common stock will go to the
stockholders who offer and sell their shares.  Accordingly,  we will not receive
any of the proceeds from sales of their shares by the selling stockholders.


                            THE SELLING STOCKHOLDERS

     This  prospectus  relates to the  resale of shares of common  stock that we
might issue to the selling stockholders in exchange or redemption for O.P. units
they held at the time of the UPREIT  transaction or acquired  subsequently under
the Pending  Projects  Acquisition  Agreement or the Berg Land  Holdings  Option
Agreement.  Most of the selling  stockholders  are members of the Berg Group. We
might issue such shares  under two  alternatives.  First,  the  exchange  rights
agreement permits every limited partner in the operating  partnerships to tender
O.P. units to us, and, at our election, to receive in exchange common stock on a
one-for-one basis at then-current market value, an equivalent amount of cash, or
a  combination  of cash and common  stock,  subject to the 9% overall  ownership
limit imposed on non-Berg Group stockholders under our charter document,  or the
overall 20% Berg Group ownership  limit contained in the acquisition  agreement,
as the case may be.  This  exchange  ratio is  subject to  adjustment  for stock
splits, stock dividends, recapitalizations of our common stock and similar types
of corporate actions.  In addition,  once in each 12-month period beginning each
December  29, the limited  partners,  other than Carl E. Berg and Clyde J. Berg,
may exercise a put right to sell their O.P. units to the operating  partnerships
at a price  equal to the  average  market  price  of the  common  stock  for the
10-trading  day  period  immediately  preceding  the  date of  tender.  Upon any
exercise of the put rights, we will have the opportunity for a period of 15 days
to elect to fund the purchase of the O.P. units and purchase  additional general
partner  interests in the operating  partnerships for cash,  unless the purchase
price exceeds $1.0 million in the aggregate for all tendering  limited partners,
in which  case,  the  operating  partnerships  or we will be  entitled,  but not
required,  to reduce proportionally the number of O.P. units to be acquired from
each tendering limited partner so that the total purchase price is not more than
$1 million.

     Under the exchange rights agreement, the holders of not less than 5% of the
O.P.  units are able to request resale  registrations  of shares of common stock
acquired  on exchange of O.P.  units on a Form S-3,  or any  equivalent  form of
registration  statement.  We are  obligated  to  effect  no more  than  two such
registrations in any 12-month  period.  We are obligated to assist the O.P. Unit
holders in obtaining a firm  commitment  underwriting  agreement for such resale
from a qualified  investment-banking  firm. If  registration  on Form S-3, or an
equivalent  form, is not available for any reason,  we are obligated to effect a
registration  of the shares to be acquired on exercise of the exchange rights on
a Form S-11  registration  statement,  or an equivalent form, in an underwritten
public offering, upon demand by the holders of no fewer than 500,000 O.P. units.
All holders of O.P. units are entitled to participate in such  registration.  We
have agreed to bear all costs of such registrations other than selling expenses,
including  commissions and separate counsels' fees of the O.P. unit holders.  We
are not  required  to  effect  any  registration  for  resale  on Form  S-3,  or
equivalent  form of shares of common stock issuable to the holders of O.P. units
if the request is for less than 250,000 shares.

     If we determine, in our sole discretion, that it would be detrimental to us
or our  stockholders  to offer or sell, or continue to offer or sell, any shares
of  common  stock  under  this  prospectus,   we  may  deliver  to  the  selling
stockholders  a  certificate  to this effect  signed by the President of Mission
West  Properties  stating  that in the  good  faith  judgment  of our  board  of
directors,  and  specifying  a period  of  between  10 and 120 days in which the
selling  stockholders  must suspend sales of common stock under this  prospectus
(though not  necessarily  by other means).  We may exercise this right just once
during any 12-month period.

     A total of 93,398,705  shares of our common stock  issuable in exchange for
the O.P.  units  outstanding  at July 1,  1998 and the O.P.  units to be  issued
pursuant to the pending projects acquisition agreement were registered under the
Securities Act pursuant to a  registration  statement on Form S-4 filed with the
SEC on May 15,  1998 and  declared  effective  on  November  23,  1998 (the "S-4
Registration  Statement").  The following  table sets forth certain  information
regarding the selling  stockholders and the shares of common stock  beneficially
owned by each of them. Except as otherwise  described below, none of the selling
stockholders  has held any office with,  been  employed  by, or otherwise  had a
material relationship with us or our affiliates within the past three years, and
the address of each selling  stockholder is c/o Mission West  Properties,  Inc.,
10050 Bandley Drive, Cupertino, California 95014.

                                     - 2 -




---------------------------------------------------------- --------------------- ----------------- -------------------
                                                                                                    Number of Shares
                                                                                    Number of      and Percentage of
                                                             Shares of Common       Shares of         Common Stock
               Name of Selling Stockholder                  Stock Beneficially     Common Stock       Beneficially
                                                               Owned before       Being Offered       Owned after
                                                               Offering (1)            (2)            Offering (1)
---------------------------------------------------------- --------------------- ----------------- -------------------
                                                                                              
Carl E. Berg(3)                                                  33,646,499        33,646,499

---------------------------------------------------------- --------------------- ----------------- -------------------
Clyde J. Berg(4)                                                 19,436,162        19,436,162              0

---------------------------------------------------------- --------------------- ----------------- -------------------
Clyde J. Berg, Trustee                                           13,252,925        13,252,925              0
   1981 Kara Ann Berg Trust

---------------------------------------------------------- --------------------- ----------------- -------------------
Berg & Berg Enterprises, LLC(5)                                     196,428           196,428              0

---------------------------------------------------------- --------------------- ----------------- -------------------
Berg & Berg Enterprises, Inc.(6)                                 10,789,383        10,789,383              0

---------------------------------------------------------- --------------------- ----------------- -------------------
West Coast Venture Capital, Inc.(7)                                 169,131           169,131              0

---------------------------------------------------------- --------------------- ----------------- -------------------
Kara Ann Berg(8)                                                    966,614           965,614            1,000

---------------------------------------------------------- --------------------- ----------------- -------------------
Sonya L. O'Rosky                                                  1,890,168         1,890,168              0

---------------------------------------------------------- --------------------- ----------------- -------------------
Sherri L. Zorn                                                    1,740,168         1,740,168              0

---------------------------------------------------------- --------------------- ----------------- -------------------
Thelmer G. Aalgaard                                               1,891,785         1,854,225           37,560

---------------------------------------------------------- --------------------- ----------------- -------------------
Brian Aalgaard                                                       83,291            72,179           11,112

---------------------------------------------------------- --------------------- ----------------- -------------------
Myron Crawford                                                       40,000            40,000              0

---------------------------------------------------------- --------------------- ----------------- -------------------
Steve Aberle                                                         17,900            17,900              0

---------------------------------------------------------- --------------------- ----------------- -------------------
Leighton Fargher                                                     30,000            30,000              0

---------------------------------------------------------- --------------------- ----------------- -------------------
Michael L. Knapp(9)                                                 243,502           200,114           43,388

---------------------------------------------------------- --------------------- ----------------- -------------------
Knapp Investments, L.P. (9)                                          40,438            31,438            9,000

---------------------------------------------------------- --------------------- ----------------- -------------------
JTK Trust                                                         1,755,761         1,755,761              0
     2929 Campus Drive, Suite 150
     San Mateo, CA  94403
---------------------------------------------------------- --------------------- ----------------- -------------------
----------------------------


(1)  Beneficial  ownership is  determined  in  accordance  with the rules of the
     Commission, which generally attribute beneficial ownership of securities to
     persons who possess sole or shared  voting power  and/or  investment  power
     with respect to those  securities and include  securities which such person
     has the  right to  acquire  within 60 days of  February  28,  2006.  Unless
     otherwise indicated,  the persons or entities identified in this table have
     sole  voting  and  investment  power with  respect  to all shares  shown as
     beneficially  owned by them.  Common stock  percentage  ownership  interest
     calculations are based on 18,448,791 shares  outstanding as of February 28,
     2006 and exclude all shares of common stock  issuable  upon the exercise of
     outstanding  options other than the shares so issuable within 60 days under
     options held by the named person. Based on this determination of beneficial
     ownership,  all of the  persons or entities in the table hold less than one
     percent of the common stock before and after the offering.

(2)  Assumes O.P.  units are exchanged for shares of common stock without regard
     to (i) whether the selling  stockholder has the right to exchange such O.P.
     units for shares of common stock  within 60 days of February 28, 2006,  and
     (ii) certain ownership limit provisions set forth in the Company's Articles
     of Amendment and Restatement and the acquisition agreement.

                                     - 3 -


(3)  Carl E. Berg is and has been our  Chairman  of the Board of  Directors  and
     Chief  Executive  Officer since 1997. This amount does not include any O.P.
     units or shares deemed  beneficially owned by Mr. Berg that are held by any
     of the Berg  Group  entities  listed  in this  table.  Mr.  Berg  disclaims
     beneficial  interest in any shares or O.P. units deemed  beneficially owned
     by Kara Ann Berg, his daughter, and the 1981 Kara Ann Berg Trust.

(4)  Clyde J. Berg is the  brother of Carl E. Berg.  This amount  excludes  O.P.
     units  held by Mr.  Berg as  trustee  of the 1981  Kara Ann Berg  Trust and
     shares  beneficially  owned by Sonya L.  O'Rosky  and Sherri L.  Zorn,  his
     daughters, as to which he disclaims beneficial ownership.  This amount does
     not include any O.P. units or shares deemed  beneficially owned by Mr. Berg
     that are held by any of the Berg Group Entities listed in this table.

(5)  Berg & Berg  Enterprises,  LLC is owned  15% by Carl E. Berg and 85% by the
     1981 Kara Ann Berg Trust.

(6)  Carl E. Berg is an executive  officer and director,  and Clyde J. Berg is a
     director, of Berg & Berg Enterprises,  Inc. With members of their immediate
     families,  Messrs.  Berg beneficially own, directly and indirectly,  all of
     the O.P. units held by Berg & Berg Enterprises, Inc.

(7)  Carl E. Berg and Berg & Berg  Enterprises  LLC own 100% of the  outstanding
     stock of West Coast Venture Capital, Inc.

(8)  This amount does not include any O.P. units indirectly and/or  beneficially
     owned by Kara Ann Berg  through  the 1981 Kara Ann Berg Trust or other Berg
     Group entities.

(9)  Mike Knapp is the Director of Operations of the Company.


                              PLAN OF DISTRIBUTION

     Each  selling  stockholder  and  any  of  his  or  her  pledgees,   donees,
transferees,  assignees and successors-in-interest  may, from time to time, sell
any or all of their  shares of common  stock on any  stock  exchange,  market or
trading facility on which our common stock is traded or in private transactions.
These sales may be at fixed or negotiated  prices.  The selling  stockholder may
use any one or more of the  following  methods  when  selling  shares  of common
stock:

-    ordinary brokerage transactions and transactions in which the broker-dealer
     solicits purchasers;

-    block trades in which the broker-dealer  will attempt to sell the shares as
     agent but may  position  and resell a portion of the block as  principal to
     facilitate the transaction;

-    purchases by a broker-dealer  as principal and resale by the  broker-dealer
     for its account;

-    an exchange  distribution  in accordance  with the rules of the  applicable
     exchange;

-    privately negotiated transactions;

-    broker-dealers  may agree with the selling  stockholder to sell a specified
     number of such shares at a stipulated price per share;

-    through options;

-    by pledge to secure debts and other obligations;

-    to cover short sales made pursuant to this prospectus;

-    a combination of any such methods of sale; or

-    any other method permitted pursuant to applicable law.

                                     - 4 -


     Broker-dealers  engaged by the  selling  stockholder  may arrange for other
brokers-dealers to participate in sales.  Broker-dealers may receive commissions
or discounts  from the selling  stockholder  (or, if any  broker-dealer  acts as
agent  for the  purchaser  of  shares,  from the  purchaser)  in  amounts  to be
negotiated.  The  selling  stockholder  does not expect  these  commissions  and
discounts to exceed what is customary in the types of transactions involved.

     The  selling  stockholder  may from time to time pledge or grant a security
interest in some or all of the shares  owned by them and, if they default in the
performance of their secured  obligations,  the pledgees or secured  parties may
offer and sell shares of common  stock from time to time under this  prospectus,
or  under  an  amendment  to this  prospectus  under  Rule  424(b)(3)  or  other
applicable  provision of the Securities Act amending the selling security holder
list to include  the  pledgee,  transferee  or other  successors  in interest as
selling stockholder under this prospectus.

     The selling  stockholder  also may  transfer  the shares of common stock in
other circumstances, in which case the transferees, pledgees or other successors
in  interest  will  be the  selling  beneficial  owners  for  purposes  of  this
prospectus.  This  prospectus  may also be used by  transferees  of the  selling
stockholder,  including  broker-dealers  or  other  transferees  who  borrow  or
purchase  the  shares to  settle  or close  out short  sales of shares of common
stock. The selling  stockholder will act independently of us in making decisions
with respect to the timing,  manner,  and size of each sale or non-sale  related
transfer.

     The  selling   stockholder  may  enter  into  hedging   transactions   with
broker-dealers in connection with  distributions of the shares or otherwise.  In
such transactions,  broker-dealers or other financial institutions may engage in
short  sales of the shares in the course of hedging  the  positions  they assume
with the selling stockholder. The selling stockholder may also sell shares short
and  deliver  the  shares  to  close  out  such  short  positions.  The  selling
stockholder   may  also   enter   into   option  or  other   transactions   with
broker-dealers,  which require the delivery to the  broker-dealer of the shares.
The broker-dealer may then resell or otherwise  transfer such shares pursuant to
this prospectus. The selling stockholder may also pledge or loan the shares to a
broker-dealer.  The  broker-dealer  may sell the  shares  so  loaned,  or upon a
default,  the  broker-dealer  may  sell  the  pledged  shares  pursuant  to this
prospectus.  In addition,  any shares that qualify for sale pursuant to Rule 144
may be sold under Rule 144 rather than pursuant to this prospectus.

     The selling  stockholder and any broker-dealers or agents that are involved
in selling the shares of common stock may be deemed to be "underwriters"  within
the meaning of the Securities Act in connection  with such sales. In such event,
any commissions  received by such broker-dealers or agents and any profit on the
resale  of the  shares  purchased  by  them  may be  deemed  to be  underwriting
commissions  or discounts  under the  Securities  Act.  Discounts,  concessions,
commissions and similar selling  expenses,  if any,  attributable to the sale of
shares will be borne by the selling stockholder.

     If the selling  stockholder uses this prospectus for any sale of the common
stock,  they will be  subject to the  prospectus  delivery  requirements  of the
Securities Act. The selling  stockholder  will be responsible to comply with the
applicable  provisions of the Securities Act and the Securities  Exchange Act of
1934, as amended (the "Exchange Act") and the rules and  regulations  thereunder
promulgated,  including, without limitation,  Regulation M, as applicable to the
selling  stockholder  in  connection  with  resales  of its  shares  under  this
registration statement.

     We are required to pay all fees and expenses  incident to the  registration
of the shares of common  stock,  but we will not receive any  proceeds  from the
sale of the common stock.  We have agreed to indemnify the selling  stockholders
against certain losses, claims,  damages and liabilities,  including liabilities
under the Securities Act.


                       WHERE YOU CAN FIND MORE INFORMATION

     This  prospectus is filed as a part of a Form S-3  Registration  Statement,
which  also  amends  and  updates  the  registration   statement  on  Form  S-4,
(Registration  No.  333-52835-99).  This  prospectus  does not  contain  all the
information set forth in this registration statement,  the Form S-4 registration
statement or the exhibits and schedules  thereto  filed in  accordance  with the
rules and regulations of the SEC, and we are incorporating  omitted  information
by this reference. Statements made in this prospectus concerning the contents of
any  contract,   agreement  or  other  document  filed  as  an  exhibit  to  the
registration  statement are summaries of the terms of the contracts,  agreements
or

                                     - 5 -


documents and are not necessarily  complete.  You should read each exhibit for a
more complete description of the matters involved.

     The  registration  statement  and the  exhibits  filed  with the SEC may be
inspected,  without charge,  and copies may be obtained at prescribed  rates, at
the SEC's Public Reference Room at 100 F Street, N.E.,  Washington,  D.C. 20549.
Please call the SEC at 1-800-SEC-0330  for further  information on the operation
of the Public Reference Room. The registration  statement and other  information
filed by the Company  with the SEC also are  available  at the SEC's web site at
http://www.sec.gov,   which  contained  reports,   proxy  statements  and  other
information  about us  filed  electronically.  Material  filed by us may also be
inspected at the offices of the American Stock Exchange,  86 Trinity Place,  New
York, New York.


                           INCORPORATION BY REFERENCE

     Under  SEC  rules  we  are  disclosing  additional  information  to  you by
referring to documents that we have filed  previously with the SEC.  Information
that we incorporate  by reference into this  prospectus is considered to be part
of this  prospectus,  and  information  that we file  later  with  the SEC  will
automatically update and supersede this information. We incorporate by reference
the documents listed below:

     1. Registration  Statement filed on May 15, 1998 and declared  effective on
November  23,  1998  (Registration  No.  333-52835-99)  (the  "S-4  Registration
Statement"),  and the  prospectus  dated November 23, 1998 filed pursuant to SEC
Rule 424(b)(3).

     2. Our Annual  Report on Form 10-K for fiscal year ended  December 31, 2005
filed with the SEC on March 16, 2006.

     3. The  description of the common stock  contained in the S-4  Registration
Statement.

     4. Our  current  report on Form 8-K dated  April 4, 2006 and filed with the
SEC on April 10, 2006.

     In addition,  all  documents  filed by us with the SEC pursuant to Sections
13(a),  13(c),  14 or 15(d) of the Exchange Act  subsequent  to the date of this
prospectus  and  prior  to  the  filing  of a  post-effective  amendment  to the
registration  statement  containing  this  prospectus,  which indicates that all
securities  offered have been sold or which  deregisters  all of such securities
then remaining  unsold,  shall be deemed to be incorporated by reference in this
prospectus and to be a part hereof from the  respective  dates of filing of such
documents.

     You may request a copy of these  filings,  at no cost upon  written or oral
request by writing  or  telephoning  us at the  following  address or  telephone
number:  Mission  West  Properties,   Inc.,  10050  Bandley  Drive,   Cupertino,
California 95014; Attention: President; Telephone: (408) 725-0700.

     In  addition,  you may  obtain  a copy of  these  filings  from  the SEC as
described above in the section entitled "Where You Can Find More Information."


                                  LEGAL MATTERS

     We have received an opinion of counsel from Bingham,  McCutchen,  LLP, East
Palo Alto,  California  concerning  the  validity of the shares of common  stock
offered for sale by this prospectus.  A partner of Bingham,  McCutchen,  LLP who
rendered  services with respect to this opinion  indirectly owns 6,667 shares of
common stock.


                               RECENT DEVELOPMENTS

     In March  2006,  we entered  into a lease  termination  agreement  with one
tenant with respect to a lease for  approximately  92,692  rentable  square feet
that  expires in 2006.  The tenant paid us a  termination  fee of  approximately
$676,000, which we have recorded as revenue in the current period.

                                     - 6 -


     Also,  in March 2006,  one of our tenants,  JDS  Uniphase,  entered into an
assignment of lease agreement with an unrelated party, M & M Real Estate Control
&  Restructuring,  LLC  ("M&M"),  in  connection  with leases for  approximately
252,332 rentable square feet located in San Jose, California. M&M assumed all of
JDS  Uniphase's  remaining  obligations  under these  leases,  acquired  certain
personal property of JDS Uniphase located on the premises and received a payment
of  approximately  $11,147,000.  At the same time, we entered into a consent for
assignment of lease with both parties,  and a mutual release  agreement with JDS
Uniphase,  pursuant to which all of the JDS Uniphase's  obligations  under these
leases  have been  effectively  transferred  to M&M.  For  financial  accounting
purposes,  we will report this  transaction  as a lease  termination  and record
approximately  $11,147,000  as revenue in 2006.  JDS Uniphase  continues to be a
tenant with respect to 80,641  rentable  square feet at the same  location.  M&M
must continue to perform all of the  obligations  under the assumed JDS Uniphase
leases  and has the right to  sublease  any or all of the  252,332  square  feet
vacated by JDS Uniphase  for the  remainder  of the current  lease terms,  which
expire in 2006 and 2007.

     On April 4, 2006,  the Audit  Committee  of the Board of  Directors  of the
Company  determined not to renew its  engagement of BDO Seidman,  LLP ("BDO") as
the Company's  independent  registered  public  accounting  firm, and decided to
engage Burr,  Pilger & Mayer LLP ("BPM") to serve as the  Company's  independent
registered  public accounting firm for the fiscal year ending December 31, 2006.
BDO's audit  reports on the  Company's  consolidated  financial  statements  and
management's  assessment of the effectiveness of internal control over financial
reporting and the effectiveness of internal control over financial  reporting as
of and for the years ended December 31, 2005 and 2004 did not contain an adverse
opinion or  disclaimer  of opinion,  nor were they  qualified  or modified as to
uncertainty, audit scope or accounting principles. In connection with the audits
of the  Company's  consolidated  financial  statements  for each of the two most
recent fiscal years ended December 31, 2005 and 2004 and through March 31, 2006,
there  were no  disagreements  between  the  Company  and BDO on any  matters of
accounting principles or practices,  financial statement disclosure, or auditing
scope or procedure, which disagreements,  if not resolved to the satisfaction of
BDO, would have caused BDO to make reference in connection with their opinion to
the subject matter of the disagreement.  During the two most recent fiscal years
and through March 31, 2006, there have been no "reportable events" as defined in
Regulation S-K, Item 304(a)(1)(v).

     In April 2006 the  Maryland  Supreme  Court  issued its ruling in  Republic
Properties Corporation ("RPC") v. Mission West Properties,  L.P. ("MWP"), in the
Circuit Court of Maryland for Baltimore City Case No. 24-C-00-005675. The ruling
upheld an earlier  Maryland  Appeals Court ruling in favor of MWP,  finding that
the Circuit Court of Maryland could not assert personal  jurisdiction in the RPC
suit.  All  litigation in the Maryland  portion of this dispute over the Hellyer
Avenue limited partnership is now concluded in our favor. A lawsuit in the Santa
Clara County,  California Superior Court is still unresolved, as disclosed under
Part I, Item 3 "Legal  Proceedings" in our Annual Report on Form 10-K filed with
the SEC on March 16, 2006.


                                     EXPERTS

     The  financial  statements,   schedules  and  management's  report  on  the
effectiveness  of internal  control over  financial  reporting  incorporated  by
reference  in  this  prospectus  have  been  audited  by BDO  Seidman,  LLP,  an
independent registered public accounting firm, to the extent and for the periods
set  forth  in  their  reports   incorporated  herein  by  reference,   and  are
incorporated  herein in reliance  upon such reports  given upon the authority of
said firm as experts in auditing and accounting.

                                     - 7 -


                                     PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

     The  expenses in  connection  with the  issuance  and  distribution  of the
securities being registered,  other than underwriting discounts and commissions,
are estimated as follows:



                                                                                       
                  Securities and Exchange Commission Registration Fee.....................$103,629.00
                  Legal Fees and Expenses*..................................................12,500.00
                  Accounting Fees and Expenses*..............................................7,500.00
                  Printing expenses/Transfer agent's fees*.....................................500.00

                  Total*..................................................................$124,129.00
                                                                                          -----------


* Estimated.

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS

     Section 2-418 of the Maryland  General  Corporation Law ("MGCL")  permits a
Maryland  corporation  to  include  in its  charter  a  provision  limiting  the
liability of its directors and officers to the corporation and its  stockholders
for money damages  except for liability  resulting from (a) actual receipt of an
improper  benefit or profit in money,  property or  services,  or (b) active and
deliberate  dishonesty  established by a final judgment as being material to the
cause of action.  Article IX of the Articles of  Amendment  and  Restatement  of
Mission West  Properties,  Inc. (the "Charter")  contains such a provision which
eliminates such liability to the maximum extent permitted by the MGCL.

     Section  2-418 of the MGCL  requires  a  corporation  (unless  its  charter
provides  otherwise,  which the  Charter  does not) to  indemnify  a director or
officer who has been successful,  on the merits or otherwise,  in the defense of
any  proceeding  to which he is made a party by  reason of his  service  in that
capacity.  The MGCL permits a  corporation  to indemnify  its present and former
directors  and officers,  among others,  against  judgments,  penalties,  fines,
settlements,  and reasonable  expenses  actually  incurred by them in connection
with any proceeding to which they may be made a party by reason of their service
in  those or  other  capacities  unless  it is  established  that (a) the act or
omission of the  director or officer was  material to the matter  giving rise to
the  proceeding  and (i) was  committed  in bad faith or (ii) was the  result of
active and deliberate dishonesty,  (b) the director or officer actually received
an improper  personal benefit in money,  property or services or (c) in the case
of any  criminal  proceeding,  the director or officer had  reasonable  cause to
believe  that the act or  omission  was  unlawful.  However,  under the MGCL,  a
Maryland  corporation may not indemnify for an adverse  judgment in a suit by or
in the right of the corporation or for a judgment of liability on the basis that
personal benefit was improperly  received,  unless in either case a court orders
indemnification  and then only for  expenses.  In  addition,  the MGCL permits a
corporation  to advance  reasonable  expenses to a director or officer  upon the
corporation's receipt of (a) a written affirmation by the director or officer of
his good faith  belief  that he has met the  standard of conduct  necessary  for
indemnification  by the corporation  and (b) a written  undertaking by him or on
his behalf to repay the amount paid or reimbursed by the corporation if it shall
ultimately be determined that the standard of conduct was not met.

     The Charter also authorizes  Mission West  Properties,  Inc. to the maximum
extent  permitted by Maryland law, to obligate itself to indemnify and to pay or
reimburse reasonable expenses in advance of final disposition of a proceeding to
any present or former  director  or  officer,  or any  individual  who,  while a
director of Mission  West  Properties,  Inc.  and at the request of Mission West
Properties,  Inc.,  serves  or  has  served  another  corporation,  real  estate
investment trust,  partnership,  joint venture,  trust, employee benefit plan or
any  other  enterprise  as a  director,  officer,  partner  or  trustee  of such
corporation,  real estate investment trust,  partnership,  joint venture, trust,
employee  benefit  plan or  other  enterprise  from  and  against  any  claim or
liability to which such person may become subject or which such person may incur
by reason of his  status as a present or former  director  or officer of Mission
West  Properties,  Inc.  Article  XII  of  the  Bylaws  obligates  Mission  West
Properties,  Inc., to the maximum extent permitted

                                    - II-1 -


by Maryland  law, to indemnify  and to pay or reimburse  reasonable  expenses in
advance  of final  disposition  of a  proceeding  to (i) any  present  or former
director  or  officer  who is made a party to the  proceeding  by  reason of his
service in that capacity or (ii) any individual who, while a director of Mission
West Properties, Inc. and at the request of Mission West Properties, Inc. serves
or has served another corporation,  real estate,  investment trust, partnership,
joint  venture,  trust,  employee  benefit  plan or any  other  enterprise  as a
director,  officer,  partner  or  trustee  of  such  corporation,   real  estate
investment trust,  partnership,  joint venture,  trust, employee benefit plan or
other  enterprise  and who is made a party to the  proceeding  by  reason of his
service in that  capacity.  The  Charter and Bylaws  also  permit  Mission  West
Properties,  Inc. to indemnify  and advance  expenses to any person who served a
predecessor of Mission West Properties,  Inc. in any of the capacities described
above and any  employee  or agent of  Mission  West  Properties,  Inc.  and or a
predecessor of Mission West Properties, Inc.

ITEM 16. EXHIBITS.



Exhibit
Number                        Description
-------                       -----------
           
2.1            Merger Agreement and Plan of Merger between Mission West Properties and Mission West
               Properties, Inc.(1)
3.1            Articles of Amendment and Restatement of Mission West Properties, Inc.(1)
3.2            Restated Bylaws of Mission West Properties, Inc.(1)
5.1            Opinion of Graham & James LLP regarding the validity of the securities issued by the Company
               to be exchanged in the Reincorporation Merger(2)
5.2            Opinion of Ballard Spahr Andrews & Ingersoll LLP regarding the validity of securities issued
               by Mission West-Maryland in the Reincorporation Merger(2)
5.3            Opinion of Bingham, McCutchen LLP regarding the validity of the shares of common stock offered
               for sale pursuant to this registration statement.
10.1.1         Amended and Restated Agreement of Limited Partnership of Mission West Properties, L.P. (3)
10.1.2         Amended and Restated Agreement of Limited Partnership of Mission West Properties, L.P. I(3)
10.1.3         Amended and Restated Agreement of Limited Partnership of Mission West Properties, L.P. II(3)
10.1.4         Amended and Restated Agreement of Limited Partnership of Mission West Properties, L.P. III(3)
10.2           Exchange Rights Agreement between Mission West Properties, Inc. and the limited partners in
               the limited partnerships(3)
10.4.1         Acquisition Agreement, dated as of May 14, 1998, among Mission West Properties, Inc., Certain
               Partnerships and the Berg Group(1)
10.4.2         Amendment to Acquisition Agreement, dated as of July 1, 1998(1)
10.6           Pending Projects Acquisition Agreement among Mission West Properties, Inc., the Operating
               Partnership and the members of the Berg Group(3)
10.7           Berg Land Holdings Option Agreement  between Mission West Properties, Inc. and certain members
               of the Berg Group(3)
23.1           Consent of Graham & James LLP (included  in the opinion referenced in Exhibit 5.1)
23.2           Consent of Ballard Spahr Andrews & Ingersoll LLP (included in the opinion referenced in
               Exhibit 5.2)
23.3           Consent of BDO Seidman, LLP, Independent Registered Public Accounting Firm
23.4           Consent of Bingham, McCutchen LLP (included in the opinion referenced in Exhibit 5.3)
24.1           Powers of Attorney (included in the signature page to this registration statement)
------------------------


                                    - II-2 -


(1)  Incorporated  herein  by  reference  to the  same-numbered  exhibit  to the
     Company's  Registration  Statement on Form S-4/A filed on July 20, 1998 and
     declared effective on November 23, 1998.

(2)  Incorporated  herein  by  reference  to the  same-numbered  exhibit  to the
     Registration  Statement  on Form  S-4/A  filed  on  November  20,  1998 and
     declared effective on November 23, 1998.

(3)  Incorporated  herein  by  reference  to the  same-numbered  exhibit  to the
     Company's  Post-effective Amendment No. 1 to Registration Statement on Form
     S-4  filed  on  Form  S-3  on  February  11,  1999   (Commission  File  No.
     333-52835-99)

ITEM 17. UNDERTAKINGS

     (a)  The undersigned Registrant hereby undertakes:

          (1)  To file,  during  any  period in which  offers or sales are being
               made, a post-effective amendment to this registration statement:

               (i)  To include any  prospectus  required by Section  10(a)(3) of
                    the Securities Act of 1933.

               (ii) To reflect  in the  prospectus  any facts or events  arising
                    after the effective date of the  registration  statement (or
                    the most recent  post-effective  amendment  thereof)  which,
                    individually  or in the  aggregate,  represent a fundamental
                    change  in the  information  set  forth in the  registration
                    statement.  Notwithstanding  the foregoing,  any increase or
                    decrease  in  volume  of  securities  offered  (if the total
                    dollar  value of  securities  offered  would not exceed that
                    which was registered) and any deviation from the low or high
                    end of the estimated maximum offering range may be reflected
                    in the form of prospectus filed with the Commission pursuant
                    to Rule 424(b) if, in the  aggregate,  the changes in volume
                    and price  represent no more than a 20 percent change in the
                    maximum   aggregate   offering   price   set  forth  in  the
                    "Calculation  of  Registration  Fee" table in the  effective
                    registration statement;

               (iii) To include any  material  information  with  respect to the
                    plan  of  distribution  not  previously   disclosed  in  the
                    registration  statement  or  any  material  change  to  such
                    information in the registration statement;

     PROVIDED,  HOWEVER, that paragraphs  (a)(1)(i),  (a)(1)(ii) and (a)(1)(iii)
above do not apply if the registration  statement is on Form S-3 or Form F-3 and
the information  required to be included in a post-effective  amendment by those
paragraphs is contained in reports filed with or furnished to the  Commission by
the Registrant pursuant to Section 13 or 15(d) of the Securities Exchange Act of
1934 that are  incorporated by reference in the  registration  statement,  or is
contained in a form of prospectus  filed pursuant to Rule 424(b) that is part of
the registration statement.

          (2)  That,  for the purpose of  determining  any  liability  under the
               Securities Act of 1933, each such post-effective  amendment shall
               be  deemed to be a new  registration  statement  relating  to the
               securities  offered therein,  and the offering of such securities
               at that time shall be deemed to be the initial bona fide offering
               thereof.

          (3)  To  remove  from   registration  by  means  of  a  post-effective
               amendment any of the  securities  being  registered  which remain
               unsold at the termination of the offering.

          (4)  That,  for  the  purpose  of  determining   liability  under  the
               Securities Act of 1933 to any purchaser:

               (i)  If the Registrant is relying on Rule 430B:

                    (A)  Each  prospectus  filed by the  Registrant  pursuant to
                         Rule  424(b)(3)  shall  be  deemed  to be  part  of the
                         registration   statement  as  of  the  date  the  filed
                         prospectus  was  deemed  part  of and  included  in the
                         registration statement; and

                                    - II-3 -


                    (B)  Each  prospectus  required to be filed pursuant to Rule
                         424(b)(2),  (b)(5), or (b)(7) as part of a registration
                         statement  in  reliance  on Rule  430B  relating  to an
                         offering made pursuant to Rule 415(a)(1)(i),  (vii), or
                         (x)  for  the  purpose  of  providing  the  information
                         required by Section 10(a) of the Securities Act of 1933
                         shall  be  deemed  to be  part of and  included  in the
                         registration  statement  as of the  earlier of the date
                         such   form  of   prospectus   is  first   used   after
                         effectiveness or the date of the first contract of sale
                         of  securities   in  the  offering   described  in  the
                         prospectus.  As  provided in Rule 430B,  for  liability
                         purposes  of the issuer and any person  that is at that
                         date an underwriter,  such date shall be deemed to be a
                         new  effective  date  of  the  registration   statement
                         relating  to  the   securities   in  the   registration
                         statement  to which that  prospectus  relates,  and the
                         offering  of such  securities  at that  time  shall  be
                         deemed to be the initial  bona fide  offering  thereof.
                         Provided,   however,   that  no  statement  made  in  a
                         registration  statement or  prospectus  that is part of
                         the  registration  statement  or  made  in  a  document
                         incorporated  or deemed  incorporated by reference into
                         the  registration  statement or prospectus that is part
                         of the  registration  statement will, as to a purchaser
                         with a time of contract of sale prior to such effective
                         date,  supersede or modify any statement  that was made
                         in the  registration  statement or prospectus  that was
                         part of the registration  statement or made in any such
                         document immediately prior to such effective date; or

               (ii) If the Registrant is subject to Rule 430C,  each  prospectus
                    filed  pursuant  to Rule  424(b)  as part of a  registration
                    statement  relating to an offering,  other than registration
                    statements  relying on Rule 430B or other than  prospectuses
                    filed in reliance  on Rule 430A,  shall be deemed to be part
                    of and included in the registration statement as of the date
                    it is first used  after  effectiveness.  Provided,  however,
                    that  no  statement  made  in a  registration  statement  or
                    prospectus  that is part of the  registration  statement  or
                    made in a document  incorporated  or deemed  incorporated by
                    reference into the registration statement or prospectus that
                    is  part  of  the  registration  statement  will,  as  to  a
                    purchaser  with a time of  contract  of sale  prior  to such
                    first use,  supersede or modify any statement  that was made
                    in the registration statement or prospectus that was part of
                    the  registration  statement  or made in any  such  document
                    immediately prior to such date of first use.

          (5)  That, for the purpose of determining  liability of the Registrant
               under the  Securities Act of 1933 to any purchaser in the initial
               distribution of the securities:

               The undersigned  Registrant undertakes that in a primary offering
               of  securities  of the  undersigned  Registrant  pursuant to this
               registration  statement,  regardless of the  underwriting  method
               used to sell the securities to the  purchaser,  if the securities
               are  offered  or sold to such  purchaser  by  means of any of the
               following  communications,  the undersigned  Registrant will be a
               seller to the  purchaser  and will be considered to offer or sell
               such securities to such purchaser:

               (i)  Any preliminary  prospectus or prospectus of the undersigned
                    Registrant  relating  to the  offering  required to be filed
                    pursuant to Rule 424;

               (ii) Any  free  writing  prospectus   relating  to  the  offering
                    prepared by or on behalf of the  undersigned  Registrant  or
                    used or referred to by the undersigned Registrant;

               (iii) The portion of any other free writing  prospectus  relating
                    to the offering  containing  material  information about the
                    undersigned  Registrant or its securities  provided by or on
                    behalf of the undersigned Registrant; and

               (iv) Any  other  communication  that is an offer in the  offering
                    made by the undersigned Registrant to the purchaser.

     (b)  The undersigned  Registrant  hereby  undertakes  that, for purposes of
          determining  any  liability  under the  Securities  Act of 1933,  each
          filing of the Registrant's  annual report pursuant to Section 13(a) or
          15(d) of the Securities  Exchange Act of 1934 (and, where  applicable,
          each filing of an employee  benefit  plan's annual report  pursuant to
          Section  15(d)  of the  Securities  Exchange  Act  of  1934)  that  is
          incorporated  by

                                    - II-4 -


          reference in the  registration  statement  shall be deemed to be a new
          registration statement relating to the securities offered therein, and
          the offering of such securities at that time shall be deemed to be the
          initial bona fide offering thereof.

     (c)  Insofar  as   indemnification   for  liabilities   arising  under  the
          Securities  Act of 1933 may be  permitted to  directors,  officers and
          controlling  persons  of the  Registrant  pursuant  to the  provisions
          described in Item 15 above,  or  otherwise,  the  Registrant  has been
          advised that in the opinion of the Securities and Exchange  Commission
          such  indemnification is against public policy as expressed in the Act
          and is,  therefore,  unenforceable.  In the  event  that a  claim  for
          indemnification  against such  liabilities  (other than the payment by
          the Registrant of expenses incurred or paid by a director,  officer or
          controlling  person of the Registrant in the successful defense of any
          action,  suit or proceeding) is asserted by such director,  officer or
          controlling person in connection with the securities being registered,
          the Registrant  will,  unless in the opinion of its counsel the matter
          has  been  settled  by  controlling  precedent,  submit  to a court of
          appropriate  jurisdiction the question whether such indemnification by
          it is  against  public  policy  as  expressed  in the Act and  will be
          governed by the final adjudication of such issue.


                                   SIGNATURES

     Pursuant to the  requirements of the Securities Act of 1933, the Registrant
certifies  that it has  reasonable  grounds to believe  that it meets all of the
requirements  for  filing  on Form S-3 and has  duly  caused  this  registration
statement on Form S-3 to be signed on its behalf by the  undersigned,  thereunto
duly  authorized,  in the City of  Cupertino,  State of  California on April 17,
2006.

                               Mission West Properties, Inc.

                               By:  /s/ Carl E. Berg
                                  -----------------------------
                                  Carl E. Berg
                                  Chairman of the Board, Chief Executive
                                  Officer (Principal Executive Officer)

                               By:  /s/ Wayne N. Pham
                                  -----------------------------
                                  Wayne N. Pham
                                  Vice President of Finance and Controller
                                  (Principal Accounting Officer)

                                    - II-5 -



                                POWER OF ATTORNEY

     KNOW ALL  PERSONS  BY THESE  PRESENTS,  that each  person  whose  signature
appears  below  hereby  constitutes  and  appoints  Carl E. Berg and  Raymond V.
Marino, and each one of them, acting  individually and without the other, as his
or her  attorney-in-fact,  each with full power of substitution,  for him in any
and  all  capacities,  to  sign  any and  all  amendments  to this  registration
statement  (including  post-effective  amendments),  and to file the same,  with
exhibits  thereto  and  other  documents  in  connection  therewith,   with  the
Securities  and Exchange  Commission,  hereby  ratifying and confirming all that
each of said  attorneys-in-fact or his substitute or substitutes may do or cause
to be done by virtue hereof.

     Pursuant  to  the   requirements  of  the  Securities  Act  of  1933,  this
Registration  Statement  has been signed below by the  following  persons in the
capacities indicated, effective April 17, 2006.


         Signature                       Title
         ---------                       -----


 /s/ Carl E. Berg                Chairman of the Board, Chief Executive Officer
 ---------------------------     and Director
 Carl E. Berg

 /s/ John C. Bolger              Director
 ---------------------------
 John C. Bolger

 /s/ William A. Hasler           Director
 ---------------------------
 William A. Hasler

 /s/ Lawrence B. Helzel          Director
 ---------------------------
 Lawrence B. Helzel

 /s/ Raymond V. Marino           President, Chief Operating Officer and Director
 ---------------------------
 Raymond V. Marino

 /s/ Wayne N. Pham               Vice President of Finance and Controller
 ---------------------------
 Wayne N. Pham

                                    - II-6 -




EXHIBIT INDEX



Exhibit
Number                         Description
-------                        -----------
           
2.1            Merger Agreement and Plan of Merger between Mission West Properties and Mission West Properties, Inc.(1)
3.1            Articles of Amendment and Restatement of Mission West Properties, Inc.(1)
3.2            Restated Bylaws of Mission West Properties, Inc. (1)
5.1            Opinion of Graham & James LLP regarding the validity of the securities issued by the Company to
               be exchanged in the Reincorporation Merger(2)
5.2            Opinion of Ballard Spahr Andrews & Ingersoll LLP regarding the validity of securities issued by
               Mission West-Maryland in the Reincorporation Merger(2)
5.3            Opinion of Bingham, McCutchen LLP regarding the validity of the shares of common stock offered
               for sale pursuant to this registration statement.
10.1.1         Amended and Restated Agreement of Limited Partnership of Mission West Properties, L.P.(3)
10.1.2         Amended and Restated Agreement of Limited Partnership of Mission West Properties, L.P. I(3)
10.1.3         Amended and Restated Agreement of Limited Partnership of Mission West Properties, L.P. II(3)
10.1.4         Amended and Restated Agreement of Limited Partnership of Mission West Properties, L.P. III(3)
10.2           Exchange Rights Agreement between the Company and the Limited Partners(3)
10.4.1         Acquisition Agreement, dated as of May 14, 1998, among the Company, Certain Partnerships and the
               Berg Group(1)
10.4.2         Amendment to Acquisition Agreement, dated as of July 1, 1998(1)
10.6           Pending Projects Acquisition Agreement among the Company, the Operating Partnership and the
               members of the Berg Group(3)
10.7           Berg Land Holdings Option Agreement between the Company and certain members of the Berg Group(3)
23.1           Consent of Graham & James LLP (included in the opinion referenced in Exhibit 5.1)
23.2           Consent of Ballard Spahr Andrews & Ingersoll (included in the opinion referenced in Exhibit 5.2)
23.3           Consent of BDO Seidman, LLP, Independent Registered Public Accounting Firm
23.4           Consent of Bingham, McCutchen LLP (included in the opinion referenced in Exhibit 5.3)
24.1           Powers of Attorney (included in the signature page to this registration statement)

-------------------------



(1)  Incorporated  herein  by  reference  to the  same-numbered  exhibit  to the
     Company's  Registration  Statement on Form S-4/A filed on July 20, 1998 and
     declared effective on November 23, 1998.

(2)  Incorporated  herein  by  reference  to the  same-numbered  exhibit  to the
     Registration  Statement  on Form  S-4/A  filed  on  November  20,  1998 and
     declared effective on November 23, 1998.

(3)  Incorporated  herein  by  reference  to the  same-numbered  exhibit  to the
     Company's  Post-effective Amendment No. 1 to Registration Statement on Form
     S-4  filed  on  Form  S-3  on  February  11,  1999   (Commission  File  No.
     333-52835-99)

                                    - II-7 -