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


                                  SCHEDULE 13G

                    UNDER THE SECURITIES EXCHANGE ACT OF 1934
                              (AMENDMENT NO. ____)*

                              Schering-Plough Corp
-------------------------------------------------------------------------------
                                (Name of Issuer)

                                     Common
-------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    806605101
                   -------------------------------------------
                                 (CUSIP Number)

                                December 31, 2003
         --------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

[X] Rule 13d-1(b)
[_] Rule 13d-1(c)
[_] Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

                                PAGE 1 OF 4 PAGES



-------------------------                                  ---------------------
  CUSIP NO. 806605101                     13G                PAGE 2 OF 4 PAGES
-------------------------                                  ---------------------

--------------------------------------------------------------------------------
1      NAME OF REPORTING PERSON
       S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

       Dodge & Cox              94-1441976
--------------------------------------------------------------------------------
 2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*        (a) [_]
                                                                (b) [_]

       N/A
--------------------------------------------------------------------------------
 3     SEC USE ONLY

--------------------------------------------------------------------------------
 4     CITIZENSHIP OR PLACE OF ORGANIZATION

       California - U.S.A.
--------------------------------------------------------------------------------
                     5     SOLE VOTING POWER

     NUMBER OF             74,926,467
      SHARES       -------------------------------------------------------------
                     6     SHARED VOTING POWER
   BENEFICIALLY
     OWNED BY              772,100
                   -------------------------------------------------------------
       EACH          7     SOLE DISPOSITIVE POWER

    REPORTING              79,706,603
      PERSON       -------------------------------------------------------------
                     8     SHARED DISPOSITIVE POWER
       WITH
                           0
--------------------------------------------------------------------------------
 9     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

       79,706,603
--------------------------------------------------------------------------------
10     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

       N/A
--------------------------------------------------------------------------------
11     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

       5.4%
--------------------------------------------------------------------------------
12     TYPE OF REPORTING PERSON*

       IA
--------------------------------------------------------------------------------



     Item 1(a) Name of Issuer:
               Schering-Plough Corp

     Item 1(b) Address of Issuer's Principal Executive Offices:
               2000 Galloping Hill Road
               Kenilworth, NJ 07033

     Item 2(a) Name of Person Filing:
               Dodge & Cox

     Item 2(b) Address of the Principal Office or, if none, Residence:
               One Sansome St., 35th Floor
               San Francisco, CA 94104

     Item 2(c) Citizenship:
               California - U.S.A.

     Item 2(d) Title of Class of Securities:
               Common

     Item 2(e) CUSIP Number:
               806605101

     Item 3    If the Statement is being filed pursuant to Rule 13d-1(b),
               or 13d-2(b), check whether the person filing is a:

               (e)  [X] Investment Advisor registered under section 203 of
                        the Investment Advisors Act of 1940

     Item 4    Ownership:
               (a) Amount Beneficially Owned:
                   79,706,603

               (b) Percent of Class:
                   5.4%

                                PAGE 3 OF 4 PAGES



                 (c) Number of shares as to which such person has:

                 (i) sole power to vote or direct the vote:
                     74,926,467

                (ii) shared power to vote or direct the vote:
                     772,100

               (iii) sole power to dispose or to direct the
                     disposition of: 79,706,603

                (iv) shared power to dispose or to direct the
                     disposition of: 0

     Item 5    Ownership of Five Percent or Less of a Class:
               Not applicable.

     Item 6    Ownership of More than Five Percent on Behalf of Another
               Person:
               Securities reported on this Schedule 13G are beneficially owned
               by clients of Dodge & Cox, which clients may include investment
               companies registered under the Investment Company Act and/or
               employee benefit plans, pension funds, endowment funds or other
               institutional clients.

     Item 7    Identification and Classification of the Subsidiary Which
               Acquired the Security Being Reported on By the Parent Holding
               Company:
               Not applicable.

     Item 8    Identification and Classification of Members of the Group:
               Not applicable.

     Item 9    Notice of Dissolution of a Group:
               Not applicable.

     Item 10   Certification:
               By signing below I certify that, to the best of my knowledge and
               belief, the securities referred to above were acquired in the
               ordinary course of business and were not acquired for the purpose
               of and do not have the effect of changing or influencing the
               control of the issuer of such securities and were not acquired in
               connection with or as a participant in any transaction having
               such purpose or effect.

                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Dated:  February 17, 2004

                                      DODGE & COX

                                      By:    /s/ THOMAS M. MISTELE
                                         ------------------------------------
                                      Name:  Thomas M. Mistele
                                      Title: Vice President

                                PAGE 4 OF 4 PAGES