AMENDMENT NO. 5 TO SCHEDULE 13D

This Amendment No. 5 (this “Amendment”) amends the Schedule 13D previously filed by Occidental Petroleum Corporation, a Delaware corporation (“Occidental”), Occidental Petroleum Investment Co., a California corporation (“OPIC”), and Occidental Chemical Holding Corporation, a California corporation (“OCHC” and, together with Occidental and OPIC, the “Reporting Persons”), with respect to the Reporting Persons’ beneficial ownership in Lyondell Chemical Company (“Lyondell”). This Amendment is being filed to disclose a change in Item 5 to the previously filed Schedule 13D.

ITEM 4. PURPOSE OF TRANSACTION

Item 4 is restated as follows:

Other than as set forth in 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 regularly reviews and analyzes its investments and other operations, including its investments in Lyondell, in order to determine whether value for Occidental’s stockholders 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 investment, these reviews and analyses depend on a variety of factors, including, without limitation, the price of, and other market conditions relating to, the Lyondell securities, the investment return on the Lyondell securities, 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

Item 5 is amended as follows:

(a)-(b)  OCHC directly owns 20,307,860 shares of common stock (“Common Stock”) of Lyondell, representing approximately 8.2% of the issued and outstanding shares of Common Stock, and a warrant to purchase 5,000,000 shares of Common Stock as described in the Schedule 13D filed with the Securities and Exchange Commission on September 3, 2002. If OCHC exercises the warrant and Lyondell elects to deliver the shares of Common Stock instead of cash proceeds, OCHC will directly own 25,307,860 shares of Common Stock, representing approximately 10.0% of the issued and outstanding Common Stock.

As the sole stockholder of OCHC, OPIC may be deemed to be the beneficial owner of, and for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), to have the shared power to vote or direct the vote of and shared power to dispose or direct the disposition of, the 25,307,860 shares of Common Stock (including 5,000,000 shares of Common Stock issuable upon exercise of a warrant) held by OCHC.

As the sole stockholder of OPIC, Occidental may be deemed to be the beneficial owner of, and for purposes of Rule 13d-3 under the Exchange Act to have the shared power to vote or direct the vote of and shared power to dispose or direct the disposition of, the 25,307,860 shares of Common Stock (including 5,000,000 shares of Common Stock issuable upon exercise of a warrant) held by OCHC.

(c)  On November 3, 2006, OCHC sold 10,000,000 shares of Common Stock in an underwritten public offering at a price to the public of $25.50 per share. After deducting underwriting discounts and commissions, OCHC received $25.05 per share pursuant to an Underwriting Agreement

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