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                                     Prospectus Supplement No. 6 Rule 424 (b)(2)

                                                               File No. 33-65053

                                                       Dated: September 13, 1999

                                  $182,000,000
                            GATX CAPITAL CORPORATION
                          MEDIUM TERM NOTES, SERIES E
                      WITH MATURITIES FROM NINE MONTHS TO
                        FIFTEEN YEARS FROM DATE OF ISSUE



                                                             
Original Issue Date: September 15, 1999                                Floating Rate Notes

Original Issue Price: 100                                              Fixed Rate Notes XX

Total Amount OID: $16,000,000.00                                       Book Entry Notes XX

Initial Accrual Period OID:                                            Certificated Notes

Maturity Date: September 15, 2003                                      CUSIP Number: 36144T CPO

Applicable Only to Fixed Rate Notes:

        Interest Rate: 7.50%

Applicable Only to Floating Rate Notes:

        Interest Rate Basis:

        Commercial Paper Rate:                                  Maximum Interest Rate:

        __ Federal Funds Rate:                                  Minimum Interest Rate:

        __ Treasury Rate:                                       Interest Reset Date:

        __ LIBOR                                                Interest Reset Period:

        Interest Payment Date(s): April 1st and October 1st

        Initial Interest Rate:                                  Interest Payment Period: Semi Annual

        Index Maturity:                                         Calculation Date:

        Spread (plus or minus)                                  Calculation Agent: Chase Manhattan Bank

Redemption at Option of Holder: Yes __ No XXX                          Redemption Date: N/A

Redemption at Option of Company: Yes __ No XXX                         Redemption Price: N/A


The Note may be redeemed at the option of the Holder on or after the Redemption
Date and at the redemption prices indicated on this Pricing Supplement, in whole
or in part in increments of $1,000 (provided that any remaining principal amount
of this Note shall be at least $1,000), together with interest on the Note
payable to the Redemption Date, on notice given to the Trustee and the Company
at least 60 days prior to the Redemption Date.

Capitalized terms used herein and not otherwise defined herein shall have the
meanings ascribed thereto in the Prospectus. The preceding description of the
particular terms of the Notes offered hereby supplements, and to the extent
inconsistent therewith replaces, the description of the general terms and
provisions of the Notes set forth in the Prospectus, to which description
reference is hereby made.