FILED PURSUANT TO RULE 424(B)(3)
                                                     REGISTRATION NO. 333-110451
                                                                   333-110451-01



PROSPECTUS SUPPLEMENT NO. 3


                                  $125,000,000
                                GATX CORPORATION
                      5% SENIOR CONVERTIBLE NOTES DUE 2023
                     FULLY AND UNCONDITIONALLY GUARANTEED BY
                           GATX FINANCIAL CORPORATION
                           AND SHARES OF COMMON STOCK
                      ISSUABLE UPON CONVERSION OF THE NOTES

                                 --------------

     This prospectus supplement supplements the prospectus dated April 4, 2005
of GATX Corporation and GATX Financial Corporation, as supplemented by the
prospectus supplement No. 1 dated May 9, 2005 and the prospectus supplement No.
2 dated June 23, 2005, relating to the sale by certain holders of our 5% Senior
Convertible Notes due 2023 and the shares of GATX Corporation common stock
issuable upon conversion of the notes. You should read this prospectus
supplement in conjunction with the prospectus. This prospectus supplement is
qualified by reference to the prospectus except to the extent that the
information in this prospectus supplement supersedes the information contained
in the prospectus. Capitalized terms used in this prospectus supplement and not
otherwise defined herein have the meanings specified in the prospectus.

     The table of Selling Holders contained in the prospectus is hereby amended
to add the entity named below as a Selling Holder:




Name                                                        PRINCIPAL AMOUNT OF NOTES     NUMBER OF SHARES OF
                                                                BENEFICIALLY OWNED            COMMON STOCK
                                                                 THAT MAY BE SOLD           THAT MAY BE SOLD
                                                                 ----------------           ----------------
                                                                                    
Credit Suisse First Boston Europe Ltd ..................             7,000,000                   288,850




     INVESTING IN THE NOTES AND OUR COMMON STOCK INVOLVES RISKS. SEE "RISK
FACTORS" BEGINNING ON PAGE 5 OF THE PROSPECTUS.

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     NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE
ACCURACY OR ADEQUACY OF THE PROSPECTUS OR THIS PROSPECTUS SUPPLEMENT. ANY
REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

                                 --------------

            The date of this prospectus supplement is July 22, 2005.