Exhibit 8.1


                     [LETTERHEAD OF MAYER, BROWN & PLATT]

                                January 16, 1998


Clark Refining & Marketing, Inc.
8182 Maryland Avenue
St. Louis, Missouri 63105

     Re:  Clark Refining & Marketing, Inc.
     Registration Statement on Form S-4
     ----------------------------------

Dear Ladies and Gentlemen:

     We have acted as counsel to Clark Refining & Marketing, Inc., a Delaware
corporation (the "Company"), in connection with the preparation and filing with
the Securities and Exchange Commission under the Securities Act of 1933, as
amended, of a Registration Statement on Form S-4 (the "Registration Statement")
relating to the Company's 8 3/8% New Senior Notes due November 15, 2007 (the
"New Senior Notes") and 8 7/8% New Senior Subordinated Notes due November 15,
2007 (the "New Senior Subordinated Notes") to be issued under the respective
indentures, dated as of November 21, 1997, between the Company and Bankers Trust
Company as trustee for the New Senior Notes, and Marine Midland Bank as trustee
for the New Senior Subordinated Notes. Capitalized terms used herein but not
otherwise defined are used as defined in the Registration Statement.

     In connection with the registration of the New Senior Notes and the New
Senior Subordinated Notes, you have requested our opinion concerning the
information in the Registration Statement under the heading "CERTAIN U.S.
FEDERAL INCOME TAX CONSIDERATIONS."

     In formulating our opinion, we have reviewed and relied upon the
Registration Statement, other documents and information provided by you, and
such applicable provisions of law including the Internal Revenue Code of 1986,
as amended (the "Code") and other records, instruments, certificates and
documents as we have considered necessary or desirable to enable us to express
the opinion set forth below. For purposes of our opinion, we have not made an
independent investigation of the facts set forth in such documents including the
Registration Statement. We have consequently relied upon representations that
the information presented therein or otherwise forwarded to us accurately and
completely describe all material facts. No facts have come to our attention,
however that would cause us to question the accuracy or completeness of such
facts or documents in or material used.

     In rendering this opinion, we have assumed that the transactions
contemplated by the foregoing documents will be consummated in accordance with
the operative documents, and that such documents accurately reflect the material
facts of such transactions.  In addition, the opinion set forth below is based
on the correctness of the assumption that there has been no change in the Code,
the regulations promulgated thereunder by the Treasury Department, and the
interpretation of the Code and such regulations by the courts and the Internal
Revenue Service, all as they are in effect and exist at the date of this letter.
With respect to this assumption it should be noted that statutes, regulations,
judicial decisions and administrative interpretations are subject to change at
any time and, in some circumstances, with retroactive effect.  A material change
that is made after the date hereof in any of the foregoing bases for our
opinion, could affect our conclusion.
 
     Based upon and subject to the foregoing, it is our opinion that the
information in the Registration Statement under the heading "CERTAIN U.S.
FEDERAL INCOME TAX CONSIDERATIONS", to the extent that it constitutes matters of
law or legal conclusions, has been reviewed by us and is correct in all material
respects.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                   Very truly yours,

                                   /s/ Mayer, Brown & Platt

                                   Mayer, Brown & Platt