[MAYER, BROWN, ROWE & MAW LETTERHEAD]



                                                                     Exhibit 8.1

                                  May 13, 2003


GATX Financial Corporation
500 West Monroe Street
Chicago, Illinois 60661

         Re:      Shelf Registration of $1,000,000,000 of
                  Debt Securities and Pass Through Certificates

Ladies and Gentlemen:

         We have acted as counsel to GATX Financial Corporation, 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 shelf Registration Statement on Form S-3 (the "Registration
Statement"). The Registration Statement relates to up to $1,000,000,000
aggregate principal amount of debt securities and pass through certificates (the
"Pass Through Certificates") that may be issued in one or more series from time
to time on a delayed basis.

         In rendering this opinion, we have relied upon the Internal Revenue
Code of 1986, as amended, legislative history, Treasury regulations, judicial
authorities, published positions of the Internal Revenue Service and such other
authorities as we have considered relevant, all as in effect on the date hereof
and all of which are subject to change, which change may be retroactive, or
different interpretations, which interpretations may have retroactive
application. This opinion is subject to the explanations and qualifications set
forth under the caption "Federal Income Tax Consequences" in the prospectus
relating to the Pass Through Certificates which constitutes a part of the
Registration Statement (the "Prospectus").

         On the basis of and subject to the foregoing, we confirm that the
discussion set forth in the Prospectus relating to the Pass Through Certificates
under the caption "Federal Income Tax Consequences" accurately summarizes the
material federal income tax consequences to U.S. holders of the ownership and
disposition of the Pass Through Certificates except to the extent that the
characteristics of any series of Pass Through Certificates differs from the
characteristics described in the Prospectus.





GATX Financial Corporation
May 13, 2003
Page 2


         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and the use of our name under the caption "Federal
Income Tax Consequences" in the Prospectus relating to the Pass Through
Certificates which constitutes a part of the Registration Statement.

                                              Very truly yours,

                                              /s/  Mayer, Brown, Rowe & Maw

                                              MAYER, BROWN, ROWE & MAW