SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  Schedule 13D

                    Under the Securities Exchange Act of 1934

                                 Amendment No. 1


                            Lyondell Chemical Company
          ------------------------------------------------------------
                                (Name of Issuer)


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


                                 not applicable
          ------------------------------------------------------------
                                 (CUSIP Number)


                            Donald P. de Brier, Esq.
                        Occidental Petroleum Corporation
                            10889 Wilshire Boulevard
                          Los Angeles, California 90024
                                 (310) 208-8800
          ------------------------------------------------------------
            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)


                                  June 30, 2003
          ------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-l(e), 13d-1(f) or 13d-1(g), check the following box
[ ]


                               Page 1 of 13 Pages



                            CUSIP No. not applicable
                                      --------------


                                                              
(1)  Names of reporting persons.                                 Occidental Petroleum Corporation
     I.R.S. Identification Nos. of above persons (entities       95-4035997
     only).

(2)  Check the appropriate box if a member of a group            (a)

     (see instructions)                                          (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                         OO

(5)  Check if disclosure of legal proceedings is required
     pursuant to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                       Delaware

Number of shares beneficially owned by each reporting
person with:

     (7)  Sole voting power.                                     0

     (8)  Shared voting power.                                   40,716,792 (including 35,716,792
                                                                 shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

     (9)  Sole dispositive power.                                0

     (10) Shared dispositive power.                              40,716,792 (including 35,716,792
                                                                 shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

(11) Aggregate amount beneficially owned by each                 40,716,792 (including 35,716,792
     reporting person                                            shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

(12) Check if the aggregate amount in Row (11)
     excludes certain shares (see instructions).

(13) Percent of class represented by amount in Row               24.5%
     (11).

(14) Type of reporting person (see instructions).                CO


                               Page 2 of 13 Pages



                            CUSIP No. not applicable
                                      --------------


                                                              
(1)  Names of reporting persons.                                 Occidental Petroleum Investment
     I.R.S. Identification Nos. of above persons (entities       Co.
     only).                                                      95-2584267

(2)  Check the appropriate box if a member of a group            (a)

     (see instructions)                                          (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                         OO

(5)  Check if disclosure of legal proceedings is required
     pursuant to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                       California

Number of shares beneficially owned by each reporting
person with:

     (7)  Sole voting power.                                     0

     (8)  Shared voting power.                                   40,716,792 (including 35,716,792
                                                                 shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

     (9)  Sole dispositive power.                                0

     (10) Shared dispositive power.                              40,716,792 (including 35,716,792
                                                                 shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

(11) Aggregate amount beneficially owned by each                 40,716,792 (including 35,716,792
     reporting person                                            shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

(12) Check if the aggregate amount in Row (11)
     excludes certain shares (see instructions).

(13) Percent of class represented by amount in Row (11).         24.5%

(14) Type of reporting person (see instructions).                CO



                               Page 3 of 13 Pages



                            CUSIP No. not applicable
                                      --------------


                                                              
(1)  Names of reporting persons.                                 Occidental Chemical Holding
     I.R.S. Identification Nos. of above persons (entities       Corporation
     only).                                                      95-2865897

(2)  Check the appropriate box if a member of a group            (a)

     (see instructions)                                          (b)

(3)  SEC use only.

(4)  Source of funds (see instructions).                         OO

(5)  Check if disclosure of legal proceedings is required
     pursuant to Items 2(d) or 2(e).

(6)  Citizenship or place of organization.                       California

Number of shares beneficially owned by each reporting
person with:

     (7)  Sole voting power.                                     0

     (8)  Shared voting power.                                   40,716,792 (including 35,716,792
                                                                 shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

     (9)  Sole dispositive power.                                0

     (10) Shared dispositive power.                              40,716,792 (including 35,716,792
                                                                 shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

(11) Aggregate amount beneficially owned by each                 40,716,792 (including 35,716,792
     reporting person                                            shares of Series B Common Stock
                                                                 and 5,000,000 shares of Lyondell
                                                                 regular common stock issuable
                                                                 upon exercise of a warrant)

(12) Check if the aggregate amount in Row (11)
     excludes certain shares (see instructions).

(13) Percent of class represented by amount in Row               24.5%
     (11).

(14) Type of reporting person (see instructions).                CO



                               Page 4 of 13 Pages



ITEM 1.  SECURITY AND ISSUER.

Title of class of equity security:           Series B Common Stock
                                             Common Stock

Issuer:                                      Lyondell Chemical Company

Address of principal executive offices:      1221 McKinney Street, Suite 700
                                             Houston, Texas 77010

     This Schedule relates to the Series B Common Stock of Lyondell and a
warrant to acquire shares of the regular common stock of Lyondell. For reporting
purposes, the Reporting Person has treated the Series B Common Stock of Lyondell
as being part of the same class under Section 12 of the 1934 Act as the regular
common stock of Lyondell.


ITEM 2.  IDENTITY AND BACKGROUND.

Occidental Petroleum Corporation ("Occidental"):
------------------------------------------------

     state of organization:        Delaware

     principal business:           engaged, through its subsidiaries and
                                   affiliates, in the production, development
                                   and marketing of natural resources and
                                   chemicals

     principal business address:   10889 Wilshire Boulevard
                                   Los Angeles, California 90024

Occidental Petroleum Investment Co. ("OPIC"):
---------------------------------------------

     state of organization:        California

     principal business:           holding company

     principal business address:   10889 Wilshire Boulevard
                                   Los Angeles, California 90024

Occidental Chemical Holding Corporation ("OCHC"):
-------------------------------------------------

     state of organization:        California

     principal business:           holding company

     principal business address:   10889 Wilshire Boulevard
                                   Los Angeles, California 90024


                               Page 5 of 13 Pages



     The name, business address and current principal occupation or employment
of each of the executive officers and directors of Occidental, OPIC and OCHC
(collectively, the "Companies") are set forth below. Unless otherwise indicated,
the business address of each such person is 10889 Wilshire Boulevard, Los
Angeles, California 90024. All such persons listed below are citizens of the
United States except Mr. Syriani, who is a citizen of Lebanon; Dr. Segovia, who
is a citizen of Colombia; and Mr. Feick, who is a citizen of Canada. Unless
otherwise indicated, each occupation set forth opposite an individual's name
refers to employment with Occidental. Directors of Occidental are identified by
an asterisk (*).

Name and Business Address             Present Principal Occupation or Employment
-------------------------             ------------------------------------------

Ray R. Irani*                         Chairman of the Board and Chief Executive
                                      Officer of Occidental

Ronald W. Burkle*                     Managing Partner and majority owner of The
9130 West Sunset Boulevard            Yucaipa Companies
Los Angeles, California 90069

John S. Chalsty*                      Chairman, Muirfield Capital Management,
10 Rockefeller Center, 8th Floor      LLC
New York, New York 10020

Stephen I. Chazen                     Chief Financial Officer and Executive Vice
                                      President - Corporate Development of
                                      Occidental

Donald P. de Brier                    Executive Vice President, Secretary and
                                      General Counsel of Occidental

Edward P. Djerejian*                  Director, James A. Baker III Institute for
Rice University, MS-40                Public Policy
6100 Main Street
Houston, Texas 77005-1892

S. P. Dominick, Jr. (1)(2)            Vice President and Controller of
                                      Occidental; President of OPIC

R. Chad Dreier*                       President and Chief Executive Officer, The
24025 Park Sorrento, Suite 400        Ryland Group
Calabasas, California 91302

John E. Feick*                        President and Chief Executive Officer of
230, 319-2nd Avenue, SW               Matrix Solutions, Inc.
Calgary, Alberta, Canada T2P OC5

Richard W. Hallock                   Executive Vice President - Human Resources
                                     of Occidental


                                  Page 6 of 13



Name and Business Address             Present Principal Occupation or Employment
-------------------------             ------------------------------------------

J. R. Havert (1)(2)                   Vice President and Treasurer of
                                      Occidental; Vice President and Treasurer
                                      of OPIC; Vice President and Treasurer of
                                      OCHC

R. P. Heinkel                         Vice President of OCHC
5005 LBJ Freeway
Dallas, Texas 75244

Kenneth J. Huffman                    Vice President - Investor Relations of
                                      Occidental

Scott A. King (2)                     Vice President and General Counsel of OCHC
5005 LBJ Freeway
Dallas, Texas 75244

Dale R. Laurance*                     President of Occidental

Anthony R. Leach                      Vice President - Finance of Occidental;
                                      Executive Vice President of OCHC

Richard A. Lorraine                   Executive Vice President and Chief
5005 LBJ Freeway                      Financial Officer of OCHC
Dallas, Texas 75244

Irvin W. Maloney*                     Retired Chairman and Chief Executive
                                      Officer, Dataproducts Corporation

Robert M. McGee                       Vice President of Occidental

Lawrence P. Meriage                   Vice President - Communications and Public
                                      Affairs of Occidental

Donald L. Moore                       Vice President and Chief Information
5 East Greenway Plaza                 Officer of Occidental
Houston, Texas 77046-0504

John W. Morgan                        Executive Vice President - Operations of
                                      Occidental; Vice President of OPIC

R. Casey Olson                        Vice President of Occidental
5 East Greenway Plaza
Houston, Texas 77046-0504

Linda S. Peterson (1)                 Assistant Secretary of Occidental; Vice
                                      President and Secretary of OPIC; Vice
                                      President and Assistant Secretary of OCHC


                               Page 7 of 13 Pages



Name and Business Address             Present Principal Occupation or Employment
-------------------------             ------------------------------------------

Rodolfo Segovia*                      Member of Executive Committee of
Carrera 9A No. 99-02 OF. 1001         Inversiones Sanford
Santafe de Bogota, D.C. Colombia

Richard A. Swan                       Vice President - Health, Environment and
                                      Safety of Occidental

Aziz D. Syriani*                      President and Chief Operating Officer of
505 Park Avenue - 11th Floor          The Olayan Group
New York, New York 10022

Rosemary Tomich*                      Owner of the Hope Cattle Company and the
                                      A.S. Tomich Construction Company; Chairman
                                      of the Board of Directors and Chief
                                      Executive Officer, Livestock Clearing,
                                      Inc.

Aurmond A. Watkins, Jr.               Vice President - Tax of Occidental; Vice
                                      President of OCHC

Walter L. Weisman*                    Past Chairman and Chief Executive Officer
P.O. Box 18017                        of American Medical International, Inc.
Beverly Hills, California 90209

------------------
(1)  Director of OPIC
(2)  Director of OCHC


     During the last five years, none of the Companies or the natural persons
named above (a) has been convicted in a criminal proceeding (excluding traffic
violations or similar misdemeanors) or (b) was a party to a civil proceeding of
a judicial or administrative body of competent jurisdiction and as a result of
such proceeding was or is subject to a judgment, decree or final order enjoining
future violations of, or prohibiting or mandating activities subject to, federal
or state securities laws or finding any violation with respect to such laws.


ITEM 3.  SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

     Occidental did not transfer any funds in exchange for the 1,716,729 shares
of Series B Common Stock of Lyondell described in Item 5(c), below. The
securities constituted stock dividends.

     On August 22, 2002, Occidental paid Lyondell $440 million pursuant to a
Securities Purchase Agreement, dated as of July 8, 2002, between Lyondell and
OCHC (the "Securities Purchase Agreement") and received 34 million shares of
Series B Common Stock and 5,000,000


                               Page 8 of 13 Pages



shares of regular common stock issuable upon exercise of the Warrant for the
Purchase of Shares of Common Stock (the "Warrant").1


ITEM 4.  PURPOSE OF TRANSACTION.

     As described in Item 5(c), Occidental received 1,716,792 shares of Series B
Common Stock of Lyondell as a dividend in place of a cash dividend. Pursuant to
Lyondell's Certificate of Incorporation, Lyondell has the right to elect to pay
dividends on its Series B Common Stock with additional shares of Series B Common
Stock rather than cash.

     Directly and through OPIC and OCHC, Occidental currently holds its Lyondell
shares for investment purposes only with a view toward maximizing long-term
shareholder value for Occidental's shareholders and not for the purpose of
controlling Lyondell.

     Other than as set forth above or in Item 6 of this Schedule 13D, Occidental
currently has no plans that relate to, or would result in, any of the actions
listed in clauses (a) through (j) of Item 4 of Schedule 13D. However, Occidental
continuously reviews and analyzes its investments in each of its subsidiaries
and other operations, including the Lyondell shares, in order to determine
whether value for Occidental's shareholders is best served by holding those
investments, increasing, disposing of, or monetizing those investments, or
recapitalizing or otherwise restructuring those investments. With respect to the
Lyondell shares, these reviews and analyses depend on a variety of factors,
including without limitation, the price of, and other market conditions relating
to, the Lyondell shares, the investment return on the Lyondell shares,
Lyondell's business and prospects, other investment and business opportunities
available to Occidental, general stock market and economic conditions, tax
considerations, and other factors deemed relevant.


ITEM 5.  INTEREST IN SECURITIES OF THE ISSUER.

(a)  Occidental:    aggregate number of shares held:        40,716,792*
     -----------    percentage of class:                    24.5%

     OPIC:          aggregate number of shares held:        40,716,792*
     -----          percentage of class:                    24.5%

     OCHC:          aggregate number of shares held:        40,716,792*
     -----          percentage of class:                    24.5%


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

     1 The $440 million came from general corporate funds received when
Occidental sold to Lyondell three of its affiliates, which own a 29.5% interest
in Equistar Chemicals, LP.

     * This number includes 35,716,792 shares of Series B Common Stock and
5,000,000 shares of regular common stock issuable upon exercise of the Warrant.


                               Page 9 of 13 Pages



     None of the directors or executive officers listed in Item 2 above is the
beneficial owner of Lyondell common stock, except Ray R. Irani and Stephen I.
Chazen, each of whom holds 1,780 shares of restricted common stock, 1,780 shares
of phantom stock (to be settled for cash upon vesting of the restricted common
stock), and 1,028.0726 deferred stock units (to be settled for cash upon
retirement). Each of Dr. Irani's and Mr. Chazen's holdings constitute less than
one percent of Lyondell's common stock.


(b)  Occidental:  sole power to vote or direct the vote:             0
     -----------  shared power to vote or direct the vote:           40,716,792*
                  sole power to dispose or direct the disposition:   0
                  shared power to dispose or direct the disposition: 40,716,792*

     OPIC:        sole power to vote or direct the vote:             0
     -----        shared power to vote or direct the vote:           40,716,792*
                  sole power to dispose or direct the disposition:   0
                  shared power to dispose or direct the disposition: 40,716,792*

     OCHC:        sole power to vote or direct the vote:             0
     -----        shared power to vote or direct the vote:           40,716,792*
                  sole power to dispose or direct the disposition:   0
                  shared power to dispose or direct the disposition: 40,716,792*

     None of the directors or executive officers listed in Item 2 above is the
beneficial owner of Lyondell common stock, except Ray R. Irani and Stephen I.
Chazen, each of whom holds 1,780 shares of restricted common stock, 1,780 shares
of phantom stock (to be settled for cash upon vesting of the restricted common
stock), and 1,028.0726 deferred stock units (to be settled for cash upon
retirement). Each of Dr. Irani's and Mr. Chazen's holdings constitute less than
one percent of Lyondell's common stock.

(c)  On December 31, 2002, Occidental received a stock dividend of 568,224
shares of Series B Common Stock of Lyondell. On March 31, 2003, Occidental
received a stock dividend of 604,621 shares of Series B Common Stock of
Lyondell. On June 30, 2003, Occidental received a stock dividend of 543,947
shares of Series B Common Stock of Lyondell.

(d)  Not applicable.

(e)  Not applicable.


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

     * This number includes 35,716,792 shares of Series B Common Stock and
5,000,000 shares of regular common stock issuable upon exercise of the Warrant.


                              Page 10 of 13 Pages



ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO
SECURITIES OF THE ISSUER.

     Pursuant to the Securities Purchase Agreement, OCHC purchased from Lyondell
a total of 34,000,000 shares of Lyondell's newly created Series B common stock.
Pursuant to the Warrant, OCHC also received warrants to purchase an additional 5
million shares (the "Warrant Shares") of Lyondell's regular common stock for $25
per share. In exchange for the Lyondell securities, Occidental paid $440,000,000
in cash.

     As additional consideration for the transaction, Occidental will receive
from Lyondell a contingent payment equal to 7.38% of cash distributions from
Equistar for 2002 and 2003 up to a total of $35 million, to be paid either in
cash or in Lyondell common stock.

     Pursuant to a Stockholders Agreement, dated as of August 22, 2002 (the
"Stockholders Agreement"), Lyondell has appointed to its board of directors two
of Occidental's executive officers, Dr. Ray R. Irani (who also is an Occidental
director) and Mr. Stephen I. Chazen. Unless Occidental obtains Lyondell's
consent, the Stockholders Agreement prevents Occidental (a) from selling its
Series B common stock or the Warrant Shares and (b) from converting its Series B
common stock into regular Lyondell common stock for at least two years. In
addition, the Stockholders Agreement generally requires Occidental to vote its
Lyondell common stock in favor of the slate of directors proposed by Lyondell's
management. The Stockholders Agreement will be effective as long as Occidental
owns 17 million or more shares of Lyondell common stock.


ITEM 7.  MATERIAL TO BE FILED AS EXHIBITS.

     Exhibit 1      Agreement Pursuant to Rule 13d-1(k)

     Exhibit 2      Securities Purchase Agreement, dated as of July 8, 2002, by
                    and between Lyondell Chemical Company and Occidental
                    Chemical Holding Corporation*

     Exhibit 3      Warrant for the Purchase of Shares of Common Stock, issued
                    August 22, 2002*

     Exhibit 4      Stockholders Agreement, dated as of August 22, 2002, by and
                    among Lyondell Chemical Company and the Stockholders as
                    defined therein*


------------------
* Previously filed.


                              Page 11 of 13 Pages



                                    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.


July 3, 2003                       OCCIDENTAL PETROLEUM CORPORATION


                                   By:  /s/ J. R. HAVERT
                                        ----------------------------------------
                                        Name:     J. R. Havert
                                        Title:    Vice President and Treasurer


                                   OCCIDENTAL PETROLEUM INVESTMENT CO.


                                   By:  /s/ J. R. HAVERT
                                        ----------------------------------------
                                        Name:     J. R. Havert
                                        Title:    Vice President and Treasurer


                                   OCCIDENTAL CHEMICAL HOLDING CORPORATION


                                   By:  /s/ J. R. HAVERT
                                        ----------------------------------------
                                        Name:     J. R. Havert
                                        Title:    Vice President and Treasurer


                              Page 12 of 13 Pages