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


                                 SCHEDULE 13G


                   UNDER THE SECURITIES EXCHANGE ACT OF 1934
                              (AMENDMENT NO. __2__)*

                              Unocal Corporation
-------------------------------------------------------------------------------
                               (Name of Issuer)

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

                                   915289102
                  -------------------------------------------
                                (CUSIP Number)

                               October 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. 915289102                      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
                           24,376,044
     NUMBER OF

      SHARES       -----------------------------------------------------------
                     6     SHARED VOTING POWER
   BENEFICIALLY
                           384,000
     OWNED BY
                   -----------------------------------------------------------
       EACH          7     SOLE DISPOSITIVE POWER
                           26,234,894
    REPORTING

      PERSON       -----------------------------------------------------------
                     8     SHARED DISPOSITIVE POWER
       WITH
                           0

--------------------------------------------------------------------------------
 9     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

       26,234,894
--------------------------------------------------------------------------------
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

       10.2%

--------------------------------------------------------------------------------
12     TYPE OF REPORTING PERSON*

       IA

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

                                PAGE 2 OF 4 PAGES



          Item 1(a) Name of Issuer:
                    Unocal Corp

          Item 1(b) Address of Issuer's Principal Executive Offices:
                    2141 Rosecrans Avenue, Suite 4000
                    El Segundo, CA 90245

          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:
                    915289102

          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]  An investment advisor in accordance with section
                             240.13d-1(b)(1)(ii)(E)

          Item 4    Ownership:
                    (a)   Amount Beneficially Owned:
                          26,234,894

                    (b)   Percent of Class:
                          10.2%

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

                    (i)   sole power to vote or direct the vote:
                          24,376,044

                    (ii)  shared power to vote or direct the vote:
                          384,000

                    (iii) sole power to dispose or to direct the
                          disposition of: 26,234,894

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

                                PAGE 3 OF 4 PAGES



          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: November 7, 2003

                                      DODGE & COX

                                      By:   /S/ Thomas M. Mistele
                                         ---------------------------------------
                                      Name:  Thomas M. Mistele
                                      Title: Vice President

                                PAGE 4 OF 4 PAGES