Exhibit 5

                              [Lyondell letterhead]

May 5, 2003

Gentlemen:

     I am Senior Vice President, General Counsel and Secretary of Lyondell
Chemical Company (the "Company"). This opinion is furnished to you in connection
with the registration under the Securities Act of 1933, as amended, of 100,000
additional shares (the "Shares") of Common Stock, par value $1.00 per share, of
the Company ("Common Stock") that may be issued under the Company's Restricted
Stock Plan for Non-Employee Directors, as amended and restated effective as of
January 1, 2003 (the "Plan"). In such capacity, I am familiar with the Company's
Amended and Restated Certificate of Incorporation and Amended and Restated
Bylaws, as well as the Plan. In addition, I, or attorneys working under my
supervision, have examined records of relevant corporate proceedings with
respect to the offering of the Shares under the Plan and such other records,
instruments and documents pertaining to the Company that I have deemed necessary
for purposes of delivering this opinion. I have also examined the Company's
Registration Statement on Form S-8 to which this opinion is an exhibit
("Registration Statement"). I have assumed the genuineness of all signatures,
the legal capacity of all natural persons, the authenticity of all documents
examined as originals, the conformity to original documents of all documents
examined as certified or photostatic copies and the authenticity of the
originals of such copies.

     Based on the foregoing and having regard for such legal considerations as I
have deemed relevant, I am of the opinion that the Shares have been duly and
validly authorized for issuance and, when issued in accordance with the terms of
the Plan, will be duly and validly issued, fully paid and nonassessable.

     The foregoing opinion is limited in all respects to matters governed by the
General Corporation Law of the State of Delaware and the federal laws of the
United States of America, to the extent applicable. I hereby consent to the
filing of this opinion with the Securities and Exchange Commission as an exhibit
to the Registration Statement.

                                   Sincerely,

                                   /s/ Kerry A. Galvin

                                   Kerry A. Galvin
                                   Senior Vice President, General Counsel and
                                   Secretary