EXHIBIT 99.4

                                    FORM OF

                           LYONDELL CHEMICAL COMPANY

                               LETTER TO CLIENTS
                                      FOR
                           TENDER OF ALL OUTSTANDING

                         9 5/8% SENIOR SECURED NOTES,
                              SERIES A, DUE 2007
                          IN EXCHANGE FOR REGISTERED
                         9 5/8% SENIOR SECURED NOTES,
                              SERIES A, DUE 2007

THE EXCHANGE OFFER WILL EXPIRE AT 5:00 P.M., NEW YORK CITY TIME, ON __________,
1999, UNLESS EXTENDED (THE "EXPIRATION DATE"). OUTSTANDING NOTES TENDERED IN THE
EXCHANGE OFFER MAY BE WITHDRAWN AT ANY TIME BEFORE 5:00 P.M., NEW YORK CITY
TIME, ON THE EXPIRATION DATE FOR THE EXCHANGE OFFER.

To Our Clients:

     We are enclosing with this letter a prospectus dated       , 1999 (the
"Prospectus") of Lyondell Chemical Company (the "Issuer"), Lyondell Chemical
Worldwide, Inc. and Lyondell Chemical Nederland, Ltd. (together, the "Subsidiary
Guarantors") and the related Letter of Transmittal.  These two documents
together constitute the Issuer's offer to exchange (the "Exchange Offer") 9 5/8%
Senior Secured Notes, Series A, Due 2007 (the "New Notes"), the issuance of
which has been registered under the Securities Act of 1933, as amended (the
"Securities Act"), for a like principal amount of issued and outstanding
unregistered 9 5/8% Senior Secured Notes, Series A, Due 2007 (the "Outstanding
Notes").

     THIS LETTER TO CLIENTS AND RELATED DOCUMENTS PERTAIN ONLY TO THE ISSUER'S
OFFER TO EXCHANGE ITS 9 5/8% SENIOR SECURED NOTES, SERIES A, DUE 2007. THE
ISSUER IS CONCURRENTLY MAKING SEPARATE, INDEPENDENT OFFERS TO EXCHANGE ITS
UNREGISTERED 9 7/8% SENIOR SECURED NOTES, SERIES B, DUE 2007 AND 10 7/8% SENIOR
SUBORDINATED NOTES DUE 2009 FOR A LIKE KIND AND PRINCIPAL AMOUNT OF ITS
REGISTERED 9 7/8% SENIOR SECURED NOTES, SERIES B, DUE 2007 AND 10 7/8% SENIOR
SUBORDINATED NOTES DUE 2009, RESPECTIVELY. CLIENTS ALSO HOLDING THE ISSUER'S
9 7/8% SENIOR SECURED NOTES, SERIES B, DUE 2007 AND 10 7/8% SENIOR SUBORDINATED
NOTES DUE 2009 WHO WISH TO PARTICIPATE IN THE SEPARATE, INDEPENDENT EXCHANGE
OFFERS RELATING TO SUCH NOTES WILL NEED TO COMPLETE AND RETURN THE APPLICABLE
DOCUMENTATION RELATING TO SUCH NOTES.

     The Exchange Offer is not conditioned upon any minimum aggregate principal
amount of Outstanding Notes of that series being tendered for exchange or upon
the consummation of any other Exchange Offer.

     We are the holder of record of Outstanding Notes held by us for your own
account.  A tender of your Outstanding Notes held by us can be made only by us
as the record holder according to your instructions.  The Letter of Transmittal
is furnished to you for your information only and cannot be used by you to
tender Outstanding Notes held by us for your account.


     We request instructions as to whether you wish to tender any or all of the
Outstanding Notes held by us for your account under the terms and conditions of
the Exchange Offer.  We also request that you confirm that we may, on your
behalf, make the representations contained in the Letter of Transmittal.

     Under the Letter of Transmittal, each holder of Outstanding Notes will
represent to the Issuer that:

      (i) any New Notes received are being acquired in the ordinary course of
          business of the person receiving such New Notes;

     (ii) such person does not have an arrangement or understanding with any
          person to participate in the distribution of the Outstanding Notes or
          the New Notes within the meaning of the Securities Act;

    (iii) such person is not an "affiliate," as defined in Rule 405 under the
          Securities Act, of the Issuer or a broker-dealer tendering Outstanding
          Notes acquired directly from the Issuer for its own account;

     (iv) if such person is not a broker-dealer or is a broker-dealer but will
          not receive New Notes for its own account in exchange for Outstanding
          Notes, it is not engaged in, and does not intend to participate in, a
          distribution of New Notes; and

      (v) if such person is a broker-dealer who will receive New Notes for its
          own account in exchange for Outstanding Notes, it will represent that
          the Outstanding Notes to be exchanged for New Notes were acquired as a
          result of market-making activities or other trading activities, and it
          will acknowledge that it will deliver a Prospectus in connection with
          any resale of those New Notes; however, by so acknowledging and by
          delivering a Prospectus, it will not be deemed to admit that it is an
          "underwriter" within the meaning of the Securities Act.


                              Very truly yours,

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PLEASE RETURN YOUR INSTRUCTIONS TO US IN THE ENCLOSED ENVELOPE WITHIN AMPLE TIME
   TO PERMIT US TO SUBMIT A TENDER ON YOUR BEHALF BEFORE THE EXPIRATION DATE.


                                 INSTRUCTION TO
                            DTC TRANSFER PARTICIPANT

                To Participant of The Depository Trust Company:

     The undersigned hereby acknowledges receipt and review of the prospectus
dated     , 1999 (the "Prospectus") of Lyondell Chemical Company (the "Issuer"),
Lyondell Chemical Worldwide, Inc. and Lyondell Chemical Nederland, Ltd.
(together, the "Subsidiary Guarantors") and the related Letter of Transmittal.
These two documents together constitute the Issuer's offer to exchange (the
"Exchange Offer") 9 5/8% Senior Secured Notes, Series A, Due 2007 (the "New
Notes"), the issuance of which has been registered under the Securities Act of
1933, as amended (the "Securities Act"), for a like principal amount of issued
and outstanding unregistered 9 5/8% Senior Secured Notes, Series A, Due 2007
(the "Outstanding Notes").

     THIS LETTER TO CLIENTS AND RELATED DOCUMENTS PERTAIN ONLY TO THE ISSUER'S
OFFER TO EXCHANGE ITS 9 5/8% SENIOR SECURED NOTES, SERIES A, DUE 2007. THE
ISSUER IS CONCURRENTLY MAKING SEPARATE, INDEPENDENT OFFERS TO EXCHANGE ITS
UNREGISTERED 9 7/8% SENIOR SECURED NOTES, SERIES B, DUE 2007 AND 10 7/8% SENIOR
SUBORDINATED NOTES DUE 2009 FOR A LIKE KIND AND PRINCIPAL AMOUNT OF ITS
REGISTERED 9 7/8% SENIOR SECURED NOTES, SERIES B, DUE 2007 AND 10 7/8% SENIOR
SUBORDINATED NOTES DUE 2009, RESPECTIVELY. CLIENTS ALSO HOLDING THE ISSUER'S
9 7/8% SENIOR SECURED NOTES, SERIES B, DUE 2007 AND 10 7/8% SENIOR SUBORDINATED
NOTES DUE 2009 WHO WISH TO PARTICIPATE IN THE SEPARATE, INDEPENDENT EXCHANGE
OFFERS RELATING TO SUCH NOTES WILL NEED TO COMPLETE AND RETURN THE APPLICABLE
DOCUMENTATION RELATING TO SUCH NOTES.

     This will instruct you, the registered holder and DTC participant, as to
the action to be taken by you relating to the Exchange Offer for the Outstanding
Notes held by you for the account of the undersigned.

     The aggregate principal amount of the Outstanding Notes of each series held
by you for the account of the undersigned is (fill in amount):

          Title of Series                       Principal Amount
          ---------------                       ----------------
9 5/8% Senior Secured Notes, Series
 A, Due 2007

     WITH RESPECT TO THE EXCHANGE OFFER, THE UNDERSIGNED HEREBY INSTRUCTS YOU
(CHECK APPROPRIATE BOX):

[ ]  TO TENDER ALL OUTSTANDING NOTES HELD BY YOU FOR THE ACCOUNT OF THE
     UNDERSIGNED.

[ ]  TO TENDER THE FOLLOWING AMOUNT OF OUTSTANDING NOTES HELD BY YOU FOR THE
     ACCOUNT OF THE UNDERSIGNED:

          Title of Series                       Principal Amount Tendered
          ---------------                       -------------------------
9 5/8% Senior Secured Notes, Series
 A, Due 2007

[ ]  NOT TO TENDER ANY OUTSTANDING NOTES HELD BY YOU FOR THE ACCOUNT OF THE
     UNDERSIGNED.

                                       3


     IF NO BOX IS CHECKED, A SIGNED AND RETURNED INSTRUCTION TO DTC PARTICIPANT
WILL BE DEEMED TO INSTRUCT YOU TO TENDER ALL OUTSTANDING NOTES HELD BY YOU FOR
THE ACCOUNT OF THE UNDERSIGNED.

     If the undersigned instructs you to tender the Outstanding Notes held by
you for the account of the undersigned, it is understood that you are authorized
to make, on behalf of the undersigned (and the undersigned, by its signature
below, hereby makes to you), the representations contained in the Letter of
Transmittal that are to be made with respect to the undersigned as a beneficial
owner, including, but not limited to, the representations that:

     (i) any New Notes received are being acquired in the ordinary course of
         business of the undersigned;

    (ii) the undersigned does not have an arrangement or understanding with any
         person to participate in the distribution of the Outstanding Notes or
         the New Notes within the meaning of the Securities Act;

   (iii) the undersigned is not an "affiliate," as defined in Rule 405 under the
         Securities Act, of the Issuer or a broker-dealer tendering Outstanding
         Notes acquired directly from the Issuer for its own account;

    (iv) if the undersigned is not a broker-dealer or is a broker-dealer but
         will not receive New Notes for its own account in exchange for
         Outstanding Notes, it is not engaged in, and does not intend to
         participate in, a distribution of New Notes; and

     (v) if the undersigned is a broker-dealer that will receive New Notes for
         its own account in exchange for Outstanding Notes, it will represent
         that the Outstanding Notes to be exchanged for New Notes were acquired
         as a result of market-making activities or other trading activities,
         and it will acknowledge that it will deliver a Prospectus in connection
         with any resale of those New Notes; however, by so acknowledging and by
         delivering a Prospectus, the undersigned will not be deemed to admit
         that it is an "underwriter" within the meaning of the Securities Act.

                                   SIGN HERE

Name of beneficial owner(s):
                            -------------------------------------------------

Signature(s):
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Name(s) (please print):
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Address:
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Telephone Number:
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Taxpayer Identification or Social Security Number:
                                                  ---------------------------

Date:
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