Washington, D.C. 20549

                                    Form 13F

                               Form 13F COVER PAGE

Report for the Calendar Year or Quarter Ended:   March 31, 2003

Check here if Amendment [X]; Amendment Number:    1
     This Amendment (Check only one.):           [ ]  is a restatement.
                                                 [X]  adds new holdings entries.

Institutional Investment Manager Filing this Report:

Name:          Occidental Petroleum Corporation
Address:       10889 Wilshire Boulevard
               Los Angeles, California 90024

Form 13F File Number:  28-10313

The institutional investment manager filing this report and the person by whom
it is signed hereby represent that the person signing the report is authorized
to submit it, that all information contained herein is true, correct and
complete, and that it is understood that all required items, statements,
schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:

Name:     Stephen I. Chazen
          Chief Financial Officer and Executive Vice President -
          Corporate Development
          Occidental Petroleum Corporation
Phone:    (310) 208-8800

Signature, Place, and Date of Signing:

     /s/ STEPHEN I. CHAZEN          Los Angeles, California      May 14, 2003
     ---------------------------    -----------------------    ----------------
             [Signature]                 [City, State]              [Date]

Report Type (Check only one.):

[X]    13F HOLDINGS REPORT. (Check here if all holdings of this reporting
       manager are reported in this report.)

[ ]    13F NOTICE. (Check here if no holdings reported are in this report, and
       all holdings are reported by other reporting manager(s).)

[ ]    13F COMBINATION REPORT. (Check here if a portion of the holdings for this
       reporting manager are reported in this report and a portion are reported
       by other reporting manager(s).)

                              Form 13F SUMMARY PAGE

Report Summary:

Number of Other Included Managers:                    5
Form 13F Information Table Entry Total:               2
Form 13F Information Table Value Total:      $  232,100

List of Other Included Managers:

Provide a numbered list of the name(s) and Form 13F file number(s) of all
institutional investment managers with respect to which this report is filed,
other than the manager filing this report.

     No.       13F File Number     Name

      1           28-              Occidental C.O.B. Partners
      2           28-              Placid Oil Company
      3           28-              OXY USA Inc.
      4           28-              Occidental Oil and Gas Holding Corporation
      5           28-              Occidental Petroleum Investment Co.

                           FORM 13F INFORMATION TABLE

     COLUMN 1        COLUMN 2     COLUMN 3  COLUMN 4        COLUMN 5         COLUMN 6       COLUMN 7             COLUMN 8
----------------- -------------- --------- ---------- ------------------- -------------- ------------- -----------------------------
                                             VALUE     SHRS OR   SH/ PUT/   INVESTMENT       OTHER            VOTING AUTHORITY
 NAMES OF ISSUER  TITLE OF CLASS    CUSIP   (x$1000)   PRN AMT   PRN CALL   DISCRETION     MANAGERS    -----------------------------
                                                                                                          SOLE      SHARED    NONE
----------------- -------------- --------- ---------- ---------- --- ---- -------------- ------------- ---------- --------- --------
Premcor Inc.       Common Stock  74045Q104 $   49,022  1,908,209  SH      SOLE                          1,908,209
Premcor Inc.       Common Stock  74045Q104 $  183,078  7,126,437  SH      SHARED-DEFINED 1, 2, 3, 4, 5            7,126,437