THE INFORMATION IN THIS PRELIMINARY PROSPECTUS SUPPLEMENT IS NOT COMPLETE AND
MAY BE CHANGED. THIS PRELIMINARY PROSPECTUS SUPPLEMENT IS NOT AN OFFER TO SELL
THESE SECURITIES AND IT IS NOT SOLICITING AN OFFER TO BUY THESE SECURITIES IN
ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.



                                                FILED PURSUANT TO RULE 424(B)(3)
                                                     REGISTRATION NO. 333-145521

                  SUBJECT TO COMPLETION, DATED FEBRUARY 1, 2008

PRELIMINARY PROSPECTUS SUPPLEMENT
(TO PROSPECTUS DATED AUGUST 17, 2007)

                                   (GATX LOGO)
                                        $
                                GATX CORPORATION
                                  % SENIOR NOTES DUE

     The notes will bear interest at the rate of      % per year. Interest on
the notes is payable on            and            of each year, beginning
on           , 2008. The notes will mature on           , 20 . We may redeem
some or all of the notes at our option at any time prior to maturity at a
redemption price described under the caption "Description of Notes -- Optional
Redemption" in this prospectus supplement. If we experience a change of control
repurchase event, we may be required to offer to purchase the notes from holders
at a purchase price described under the caption "Description of
Notes -- Repurchase Upon Change of Control Repurchase Event" in this prospectus
supplement.

     The notes will be senior obligations of our company and will rank equally
with all of our other unsecured senior indebtedness.

     We do not intend to make application to list the notes on any national
securities exchange or to include them in any automated quotation system.

                                   ----------

     SEE "RISK FACTORS" BEGINNING ON PAGE S-1 OF THIS PROSPECTUS SUPPLEMENT FOR
A DISCUSSION OF CERTAIN RISK FACTORS THAT PROSPECTIVE INVESTORS SHOULD CONSIDER
BEFORE INVESTING IN THE NOTES.

     NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS
PROSPECTUS SUPPLEMENT OR THE ACCOMPANYING PROSPECTUS IS TRUTHFUL OR COMPLETE.
ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.
                                   ----------

<Table>
<Caption>
                                                           PER NOTE       TOTAL
                                                           --------     --------
                                                                  
Public offering price (1)                                  $            $
Underwriting discount                                      $            $
Proceeds to GATX Corporation (before expenses)             $            $
</Table>



- --------

(1)   Plus accrued interest, if any, from           , 2008 to the date of
      delivery.

                                   ----------

     The underwriters expect to deliver the notes to purchasers through the
facilities of The Depository Trust Company against payment in New York, New York
on or about           , 2008.

                                   ----------
                           Joint Book-Running Managers
CITI                                                                    JPMORGAN

                                   ----------
                                  Lead Manager
                         BANC OF AMERICA SECURITIES LLC

                                   ----------
                                   Co-Managers
BMO CAPITAL MARKETS                                                PIPER JAFFRAY

                                   ----------
                    Prospectus Supplement dated      , 2008.



     YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS
SUPPLEMENT, THE ACCOMPANYING PROSPECTUS AND THE DOCUMENTS WE HAVE INCORPORATED
BY REFERENCE. WE HAVE NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH DIFFERENT
INFORMATION. WE ARE NOT MAKING AN OFFER OF THE NOTES IN ANY STATE WHERE THE
OFFER OR SALE IS NOT PERMITTED. YOU SHOULD NOT ASSUME THAT THE INFORMATION
CONTAINED IN THIS PROSPECTUS SUPPLEMENT, THE ACCOMPANYING PROSPECTUS OR THE
INFORMATION WE HAVE PREVIOUSLY FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
THAT WE INCORPORATE BY REFERENCE IS ACCURATE AS OF ANY DATE OTHER THAN THEIR
RESPECTIVE DATES. IF INFORMATION IN THIS PROSPECTUS SUPPLEMENT UPDATES
INFORMATION IN THE ACCOMPANYING PROSPECTUS, THE PROSPECTUS SUPPLEMENT WILL APPLY
AND WILL SUPERSEDE THAT INFORMATION IN THE PROSPECTUS.

                                TABLE OF CONTENTS

<Table>
<Caption>
                                                                         PAGE
                                                                         ----
                                                                      
                            PROSPECTUS SUPPLEMENT
Risk Factors...........................................................   S-1
Recent Developments....................................................   S-2
Use of Proceeds........................................................   S-3
Ratio of Earnings to Fixed Charges.....................................   S-3
Selected Financial Data................................................   S-4
Forward-Looking Statements.............................................   S-5
Description of Notes...................................................   S-6
Underwriting...........................................................  S-10
Legal Opinions.........................................................  S-12
Experts................................................................  S-12
                                  PROSPECTUS
About This Prospectus..................................................     1
Disclosure Regarding Forward-Looking Statements........................     1
GATX Corporation.......................................................     1
Ratio of Earnings to Fixed Charges.....................................     2
Use of Proceeds........................................................     2
Description of Debt Securities.........................................     2
Concerning the Trustee.................................................    11
Plan of Distribution...................................................    11
Legal Opinions.........................................................    12
Experts................................................................    12
Where You Can Find More Information....................................    12
Documents Incorporated by Reference....................................    12
</Table>



In this prospectus supplement, unless the context requires otherwise, "GATX
Corporation," "we," "us," "our" and "the Company" refer to GATX Corporation and
its consolidated subsidiaries.


                                        i



                                  RISK FACTORS

     You should consider carefully the following risks, together with the other
information included or incorporated by reference in this prospectus, before
making a decision to participate in an offering for the sale of the notes.
Additional risks and uncertainties not presently known to us, or that we
currently deem immaterial, also may impair our business operations. We cannot
assure you that any of the events discussed in the risk factors below will not
occur. If they do, our business, financial condition or results of operations
could be materially and adversely affected. In such case, the trading price of
our securities, including the notes, could decline, and you might lose all or
part of your investment.

RISKS RELATING TO OUR BUSINESS

     See the risk factors set forth in GATX's Annual Report on Form 10-K for the
year ended December 31, 2006, beginning on page 6, for a discussion of certain
risks relating to our businesses.

RISKS RELATING TO THE NOTES

     THE NOTES ARE EFFECTIVELY SUBORDINATED TO THE EXISTING AND FUTURE
LIABILITIES OF OUR SUBSIDIARIES.

     The notes are our senior unsecured obligations and will rank equal in right
of payment to our other senior unsecured debt from time to time outstanding. The
notes are not secured by any of our assets. Any future claims of secured lenders
with respect to assets securing their loans will be prior to any claim of the
holders of the notes with respect to those assets.

     Our subsidiaries are separate and distinct legal entities from us. Our
subsidiaries have no obligation to pay any amounts due on the notes or to
provide us with funds to meet our payment obligations on the notes, whether in
the form of dividends, distributions, loans or other payments. In addition, any
payment of dividends, loans or advances by our subsidiaries could be subject to
statutory or contractual restrictions. Payments to us by our subsidiaries will
also be contingent upon the subsidiaries' earnings and other business
considerations. Our right to receive any assets of any of our subsidiaries upon
their bankruptcy, liquidation or reorganization, and therefore the right of the
holders of the notes to participate in those assets, will be effectively
subordinated to the claims of that subsidiary's creditors, including trade
creditors. In addition, even if we are a creditor of any of our subsidiaries,
our right as a creditor would be subordinate to any security interest in the
assets of our subsidiaries and any indebtedness of our subsidiaries senior to
that held by us.

     THE INDENTURE DOES NOT RESTRICT THE AMOUNT OF ADDITIONAL DEBT THAT WE MAY
INCUR.

     The notes and indenture under which the notes will be issued do not place
any limitation on the amount of unsecured debt that may be incurred by us. Our
incurrence of additional debt may have important consequences for you as a
holder of the notes, including making it more difficult for us to satisfy our
obligations with respect to the notes, a loss in the trading value of your
notes, if any, and a risk that the credit rating of the notes is lowered or
withdrawn.

     IF AN ACTIVE TRADING MARKET DOES NOT DEVELOP FOR THE NOTES, YOU MAY BE
     UNABLE TO SELL YOUR NOTES OR TO SELL YOUR NOTES AT A PRICE THAT YOU DEEM
     SUFFICIENT.

     The notes are new issues of securities for which there currently is no
established trading market. We do not intend to list the notes on a national
securities exchange. While the underwriters of the notes have advised us that
they intend to make a market in the notes, the underwriters will not be
obligated to do so and may stop their market-making at any time. We cannot
assure you:

     -  that a market for the notes will develop or continue;

     -  as to the liquidity of any market that does develop; or

     -  as to your ability to sell any notes you may own or the price at which
        you may be able to sell your notes.


                                       S-1



     WE MAY NOT BE ABLE TO REPURCHASE THE NOTES UPON A CHANGE OF CONTROL.

     Upon the occurrence of specific kinds of change of control events, unless
we have exercised our right to redeem the notes, each holder of notes will have
the right to require us to repurchase all or any part of such holder's notes at
a price equal to 101% of their principal amount, plus accrued and unpaid
interest, if any, to the date of purchase. If we experience a Change of Control
Repurchase Event, there can be no assurance that we would have sufficient
financial resources available to satisfy our obligations to repurchase the
notes. Our failure to purchase the notes as required under the indenture
governing the notes would result in a default under the indenture, which could
have material adverse consequences for us and the holders of the notes. See
"Description of Notes -- Repurchase Upon Change of Control Repurchase Event."

                               RECENT DEVELOPMENTS

     On January 24, 2008, we publicly announced our results of operations for
the quarter and year ended December 31, 2007.  We announced gross income of
$343.9 million for the quarter ended December 31, 2007, compared to gross income
of $318.0 million for the quarter ended December 31, 2006, and gross income of
$1,346.0 million for the year ended December 31, 2007, compared to gross income
of $1,229.1 million for the year ended December 31, 2006.  We announced income
from continuing operations for the quarter ended December 31, 2007 of $41.4
million, or $.81 per diluted share, compared to $28.7 million, or $.51 per
diluted share, for the quarter ended December 31, 2006.  We also announced
income from continuing operations for the year ended December 31, 2007 of $185.8
million, or $3.44 per diluted share, compared to $151.4 million, or $2.65 per
diluted share, for the year ended December 31, 2006.  In addition, we announced
total assets at December 31, 2007 of $4,725.6 million, compared to $4,647.0
million at December 31, 2006, total debt and capital lease obligations at
December 31, 2007 of $2,359.7 million, compared to $2,214.7 million for the year
ended December 31, 2006, and shareholders' equity at December 31, 2007 of
$1,149.5 million, compared to $1,167.7 million for the year ended December 31,
2006.

     On January 24, 2008, we also announced that our board of directors had
authorized a $200 million share repurchase program.


                                       S-2



                                 USE OF PROCEEDS

     The net proceeds to us from the sale of the notes offered by this
prospectus supplement are expected to be $          . We intend to use these net
proceeds to repay commercial paper maturing within 30 days and bearing an
effective interest rate of approximately 4.3% and for general corporate
purposes, including but not limited to working capital, capital expenditures and
repurchases of our common stock.

                       RATIO OF EARNINGS TO FIXED CHARGES

     The following table sets forth our ratio of earnings to fixed charges for
each of the periods indicated.

<Table>
<Caption>
                                         NINE MONTHS
                                            ENDED
                                        SEPTEMBER 30,          YEAR ENDED DECEMBER 31,
                                        -------------   -------------------------------------
                                         2007    2006    2006    2005    2004    2003    2002
                                        -----   -----   -----   -----   -----   -----   -----
                                                                   
Ratio of earnings to fixed charges
  (a).................................  2.10x   1.76x   1.81x   1.63x   1.83x   1.22x   1.13x
</Table>


- --------

 (a) The ratio of earnings to fixed charges represents the number of times
     "fixed charges" are covered by "earnings". "Fixed charges" consist of
     interest on outstanding debt and amortization of debt discount and expense,
     adjusted for capitalized interest and the interest portion of operating
     lease expense. "Earnings" consist of consolidated income from continuing
     operations before income taxes and fixed charges, less the share of
     affiliates' earnings, net of distributions received.


                                       S-3



                             SELECTED FINANCIAL DATA

     We have provided the following selected financial information for your
reference. The selected financial information as of and for the years ended
December 31, 2006, 2005, 2004, 2003 and 2002 is derived from our historical
consolidated financial statements audited by Ernst & Young LLP, our independent
registered public accounting firm, and incorporated by reference in this
prospectus supplement and the accompanying prospectus. Our audited historical
consolidated financial statements as of and for the years ended December 31,
2006 and 2005 are contained in our Current Report on Form 8-K filed with the
Securities and Exchange Commission on August 9, 2007, as described in Note (a)
below.

     The selected financial information as of and for the nine months ended
September 30, 2007 and 2006 is derived from our unaudited historical
consolidated financial statements incorporated by reference in this prospectus
supplement and the accompanying prospectus. See "Documents Incorporated by
Reference" in the accompanying prospectus.

<Table>
<Caption>
                                  NINE MONTHS ENDED
                                    SEPTEMBER 30                   YEAR ENDED DECEMBER 31(A)
                                 ------------------   --------------------------------------------------
                                   2007       2006      2006      2005(B)    2004(C)     2003      2002
                                 --------   -------   --------   --------   --------   -------   -------
                                                    IN MILLIONS, EXCEPT PER SHARE DATA
                                                                            
RESULTS OF OPERATIONS
Gross Income...................  $1,002.1   $ 911.1   $1,229.1   $1,103.1   $1,100.7   $ 967.9   $ 931.0
Income from continuing
  operations before cumulative
  effect of accounting change..     144.4     122.7      151.4      106.0      155.7      69.4      24.2
PER SHARE DATA
Basic:
  Income from continuing
     operations before
     cumulative effect of
     accounting change.........  $   2.86   $  2.41   $   2.97   $   2.12   $   3.15   $  1.41   $  0.49
  (Loss) income from
     discontinued operations...      0.37     (0.91)     (0.76)     (2.40)      0.29      0.16      0.23
  Cumulative effect of
     accounting change.........        --        --         --         --         --        --     (0.72)
                                 --------   -------   --------   --------   --------   -------   -------
Total..........................  $   3.23   $  1.50   $   2.21   $  (0.28)  $   3.44   $  1.57   $    --
                                 ========   =======   ========   ========   ========   =======   =======
Average number of common shares
  (in thousands)...............    50,505    50,842     51,001     50,106     49,348    49,107    48,889
Diluted:
  Income from continuing
     operations before
     cumulative effect of
     accounting change.........  $   2.63   $  2.13   $   2.65   $   1.94   $   2.80   $  1.38   $  0.49
  (Loss) income from
     discontinued operations...      0.33     (0.74)     (0.63)     (1.96)      0.24      0.15      0.23
  Cumulative effect of
     accounting change.........        --        --         --         --         --        --     (0.72)
                                 --------   -------   --------   --------   --------   -------   -------
Total..........................  $   2.96   $  1.39   $   2.02   $  (0.02)  $   3.04   $  1.53        --
                                 ========   =======   ========   ========   ========   =======   =======
Average number of common shares
  and common share equivalents
  (in thousands)...............    56,195    61,963     62,101     61,020     60,082    51,203    49,062
Dividends declared per share of
  common stock.................  $   0.72   $  0.63   $   0.84   $   0.80   $   0.80   $  1.28   $  1.28
</Table>




                                       S-4



<Table>
<Caption>
                                                                     YEAR ENDED DECEMBER 31(A)
                                   NINE MONTHS ENDED   ----------------------------------------------------
                                  SEPTEMBER 30, 2007     2006      2005(B)    2004(C)     2003       2002
                                  ------------------   --------   --------   --------   --------   --------
                                                      IN MILLIONS, EXCEPT PER SHARE DATA
                                                                                 
FINANCIAL CONDITION
Assets..........................       $4,500.9        $4,647.0   $5,247.3   $5,613.6   $6,081.7   $6,429.6
Debt and capital lease
  obligations...................        2,185.1         2,214.7    2,872.6    3,132.1    3,493.5    3,868.0
Shareholders' equity............        1,089.7         1,167.7    1,026.1    1,084.3      892.0      803.6
</Table>


- --------

 (a) During 2007, we revised our consolidated financial statements to reflect
     the retrospective application of the provisions of Financial Accounting
     Standards Board Staff Position AUG AIR-1, Accounting for Planned Major
     Maintenance Activities. This is described in more detail in Notes 2 and 25
     to our revised consolidated financial statements contained in our Current
     Report on Form 8-K filed with the Securities and Exchange Commission on
     August 9, 2007.

 (b) In 2006, GATX disposed of its Air segment. As a result, this segment has
     been segregated and classified as discontinued operations and amounts for
     all periods presented have been restated to reflect this classification.
     Additionally, continuing operations for 2005 changed from a net loss to net
     income, causing diluted EPS for 2005 to be based on a higher average common
     share equivalent.

 (c) Income from continuing operations for 2004 includes a gain on the sale of
     an idle property of $68.1 million ($37.8 million after-tax) and insurance
     recoveries of $48.4 million ($31.5 million after-tax).

                           FORWARD-LOOKING STATEMENTS

     This prospectus supplement, the accompanying prospectus and the documents
we incorporate by reference may contain statements that may constitute forward-
looking statements within the meaning of Section 27A of the Securities Act of
1933 and Section 21E of the Securities Exchange Act of 1934 (the "Exchange Act")
and are subject to the safe harbor provisions of those sections and the Private
Securities Litigation Reform Act of 1995. Some of these statements may be
identified by words such as "anticipate," "believe," "estimate," "expect,"
"intend," "predict," "project" or other words and terms of similar meaning.
Investors are cautioned that any such forward-looking statements are not
guarantees of future performance and involve risks and uncertainties, including
those described in this prospectus supplement and in our Annual Report on Form
10-K and other filings with the Securities and Exchange Commission, and that
actual results or developments may differ materially from those in the forward-
looking statements. Specific factors that might cause actual results to differ
from expectations include, but are not limited to,

     -  general economic, market, regulatory and political conditions in the
        rail, marine, industrial and other industries served by us and our
        customers;

     -  lease rates, utilization levels and operating costs in our primary asset
        segments;

     -  conditions in the capital markets;

     -  changes in our credit ratings;

     -  regulatory rulings that may impact the economic value and operating
        costs of assets;

     -  competitive factors in our primary markets including lease pricing and
        asset availability;

     -  changes in loss provision levels within our portfolio;

     -  impaired asset charges that may result from changing market conditions
        or portfolio management decisions that we implement;

     -  the outcome of pending or threatened litigation; and

     -  other factors.


                                       S-5



     Given these risks and uncertainties, readers are cautioned not to place
undue reliance on these forward-looking statements, which reflect management's
analysis, judgment, belief or expectation only as of the date hereof. We have
based these forward-looking statements on information currently available and
disclaim any intention or obligation to update or revise these forward-looking
statements to reflect subsequent events or circumstances.

                              DESCRIPTION OF NOTES

     The following description of the particular terms of the notes offered by
this prospectus supplement augments, and to the extent inconsistent replaces,
the description of the general terms and provisions of the debt securities under
"Description of Debt Securities" in the accompanying prospectus.

GENERAL

     The notes will initially be limited in aggregate principal amount to
$       . The notes will be senior securities as described in the accompanying
prospectus. We will issue the notes under an indenture dated as of           ,
2008 (the "Indenture") between us and U.S. Bank National Association, as
Trustee. The Indenture does not limit the amount of additional unsecured
indebtedness ranking equally and ratably with the notes that we may incur. We
may, from time to time, without the consent of the holders of the notes, issue
notes under the Indenture in addition, and with identical terms, to the notes
offered by this prospectus supplement. The statements in this prospectus
supplement concerning the notes and the Indenture are not complete and you
should refer to the provisions in the Indenture, which are controlling. Whenever
we refer to provisions of the Indenture, those provisions are incorporated in
this prospectus supplement by reference as a part of the statements we are
making, and the statements are qualified in their entirety by these references.

MATURITY

     The notes will mature on           ,     .

INTEREST

     The notes will bear interest at the rate of      % per year. Interest will
accrue from           , 2008 or from the most recent date to which interest has
been paid or provided for. We will pay interest on            and            of
each year to the person in whose name the note is registered at the close of
business on the preceding        or       , respectively, except that the
interest payable on the maturity date, or, if applicable, upon redemption, will
be payable to the person to whom the principal on the note is payable. We will
make the first payment on           , 2008.

     Interest on the notes will be computed on the basis of a 360-day year of
twelve 30-day months. Payments of interest and principal will be made in United
States dollars.

RANKING

     The notes will be senior obligations of our company and will rank equally
with all of our other unsecured senior indebtedness.

DENOMINATIONS

     The authorized denominations of the notes will be $1,000 or any amount in
excess of $1,000 which is an integral multiple of $1,000. No service charge will
be made for any registration of transfer or exchange of the notes, but we may
require payment of a sum sufficient to cover any tax or other governmental
charges that may be imposed in connection with the transaction.


                                       S-6



OPTIONAL REDEMPTION

     The notes will be redeemable, in whole at any time or in part from time to
time, at our option at a redemption price equal to the greater of:

     (i)   100% of the principal amount of the notes to be redeemed; and

     (ii)  the sum of the present values of the remaining scheduled payments of
           principal and interest on the notes (exclusive of interest accrued to
           the date of redemption) discounted to the date of redemption on a
           semi-annual basis (assuming a 360-day year consisting of twelve 30-
           day months) at the Adjusted Treasury Rate (as defined below),
           plus            basis points,

plus, in each case, accrued and unpaid interest thereon to the date of
redemption, all as certified to the Trustee by the Quotation Agent.

     "Adjusted Treasury Rate" means, with respect to any redemption date, the
rate per year equal to the semi-annual equivalent yield to maturity of the
Comparable Treasury Issue, assuming a price for the Comparable Treasury Issue
(expressed as a percentage of its principal amount) equal to the Comparable
Treasury Price for the redemption date.

     "Business Day" means any day other than a Saturday or Sunday and other than
a day on which banking institutions in Chicago, Illinois, Hartford, Connecticut
or New York, New York, are authorized or obligated by law or executive order to
close.

     "Comparable Treasury Issue" means the United States Treasury security
selected by the Quotation Agent as having a maturity comparable to the remaining
term of the notes to be redeemed that would be used, at the time of selection
and in accordance with customary financial practice, in pricing new issues of
corporate debt securities of comparable maturity to the remaining term of such
notes.

     "Comparable Treasury Price" means, with respect to any redemption date, the
average of the Reference Treasury Dealer Quotations for that redemption date.

     "Quotation Agent" means any of the Reference Treasury Dealers appointed by
us, as certified to the Trustee by us.

     "Reference Treasury Dealer" means each of (i) Citigroup Global Markets Inc.
and (ii) J.P. Morgan Securities Inc. and their respective successors; provided,
however, that if any of the foregoing shall cease to be a primary U.S.
Government securities dealer in New York City (a "Primary Treasury Dealer"), we
will substitute for it another nationally recognized investment bank that is a
Primary Treasury Dealer.

     "Reference Treasury Dealer Quotations" means, with respect to each
Reference Treasury Dealer and any redemption date, the average, as determined by
the Quotation Agent, of the bid and asked prices for the Comparable Treasury
Issue (expressed in each case as a percentage of its principal amount) quoted in
writing to the Quotation Agent at 5:00 p.m., New York City time, on the third
Business Day preceding such redemption date.

     We will mail notice of a redemption to holders of notes by first-class mail
at least 30 and not more than 60 days prior to the date fixed for redemption. If
fewer than all of the notes are to be redeemed, the trustee will select, not
more than 60 days prior to the redemption date, the particular notes or portions
thereof for redemption from the outstanding notes not previously called by such
method as the trustee deems fair and appropriate.

REPURCHASE UPON CHANGE OF CONTROL REPURCHASE EVENT

     Upon the occurrence of a Change of Control Repurchase Event, unless we have
exercised our right to redeem the notes as described under "-- Optional
Redemption", the Indenture provides that each holder of notes will have the
right to require us to purchase all or a portion of such holder's notes pursuant
to the offer described below (the "Change of Control Offer"), at a purchase
price equal to 101% of the principal amount

                                       S-7



thereof plus accrued and unpaid interest, if any, to the date of purchase,
subject to the rights of holders of notes on the relevant record date to receive
interest due on the relevant interest payment date.

     Within 30 days following the date upon which the Change of Control
Repurchase Event occurred, or at our option, prior to any Change of Control but
after the public announcement of the pending Change of Control, we will be
required to send, by first class mail, a notice to each holder of notes, with a
copy to the trustee, which notice will govern the terms of the Change of Control
Offer. Such notice will state, among other things, the purchase date, which must
be no earlier than 30 days nor later than 60 days from the date such notice is
mailed, other than as may be required by law (the "Change of Control Payment
Date"). The notice, if mailed prior to the date of consummation of the Change of
Control, will state that the Change of Control Offer is conditioned on the
Change of Control being consummated on or prior to the Change of Control Payment
Date.

     Holders of notes electing to have notes purchased pursuant to a Change of
Control Offer will be required to surrender their notes, with the form entitled
"Option of Holder to Elect Purchase" on the reverse of the note completed, to
the paying agent at the address specified in the notice, or transfer their notes
to the paying agent by book-entry transfer pursuant to the applicable procedures
of the paying agent, prior to the close of business on the third Business Day
prior to the Change of Control Payment Date.

     We will not be required to make a Change of Control Offer if a third party
makes such an offer in the manner, at the times and otherwise in compliance with
the requirements for such an offer made by us and such third party purchases all
notes properly tendered and not withdrawn under its offer.

     "Below Investment Grade Rating Event" means the rating on the notes is
lowered by each of the Rating Agencies and the notes are rated Below Investment
Grade by each of the Rating Agencies on any date from the date of the public
notice of an arrangement that could result in a Change of Control until the end
of the 60-day period following public notice of the occurrence of a Change of
Control (which period shall be extended so long as the rating of the notes is
under publicly announced consideration for possible downgrade by any of the
Rating Agencies); provided that a Below Investment Grade Rating Event otherwise
arising by virtue of a particular reduction in rating shall not be deemed to
have occurred in respect of a particular Change of Control (and thus shall not
be deemed a Below Investment Grade Rating Event for purposes of the definition
of Change of Control Repurchase Event hereunder) if any of the Rating Agencies
making the reduction in rating to which this definition would otherwise apply
does not announce or publicly confirm or inform the trustee in writing at its
request that the reduction was the result, in whole or in part, of any event or
circumstance comprised of or arising as a result of, or in respect of, the
applicable Change of Control (whether or not the applicable Change of Control
shall have occurred at the time of the Below Investment Grade Rating Event).

     "Change of Control" means the occurrence of any one of the following:

           -  the direct or indirect sale, lease, transfer, conveyance or other
              disposition (other than by way of merger or consolidation), in one
              or a series of related transactions, of all or substantially all
              of the assets of the Company and its subsidiaries taken as a whole
              to any "person" (as that term is used in Section 13(d)(3) of the
              Exchange Act) other than to the Company or one of its
              subsidiaries;

           -  the consummation of any transaction (including without limitation,
              any merger or consolidation) the result of which is that any
              "person" (as that term is used in Section 13(d)(3) of the Exchange
              Act) becomes the "beneficial owner" (as defined in Rules 13d-3 and
              13d-5 under the Exchange Act), directly or indirectly, of more
              than 50% of the outstanding Voting Stock of the Company, measured
              by voting power rather than number of shares;

           -  we consolidate with, or merge with or into, any Person, or any
              Person consolidates with, or merges with or into, us, in any such
              event pursuant to a transaction in which any of our outstanding
              Voting Stock or that of such other Person is converted into or
              exchanged for cash, securities or other property, other than any
              such transaction where the shares of our Voting Stock outstanding
              immediately prior to such transaction constitute, or are converted
              into or

                                       S-8



              exchanged for, a majority of the Voting Stock of the surviving
              Person immediately after giving effect to such transaction;

           -  the first day on which the majority of the members of our board of
              directors cease to be Continuing Directors; or

           -  the adoption of a plan relating to our liquidation or dissolution.

     "Change of Control Repurchase Event" means the occurrence of both a Change
of Control and a Below Investment Grade Rating Event.

     "Continuing Director" means, as of any date of determination, any member of
our board of directors who:

           -  was a member of our board of directors on the date of the
              Indenture; or

           -  was nominated for election or elected to our board of directors
              with the approval of a majority of the Continuing Directors who
              were members of such board of directors at the time of such
              nomination or election.

     "Investment Grade" means a rating of Baa3 or better by Moody's (or its
equivalent under any successor rating category of Moody's); and a rating of BBB-
or better by S&P (or its equivalent under any successor rating category of S&P).

     "Moody's" means Moody's Investors Service, Inc., a subsidiary of Moody's
Corporation, and its successors.

     "S&P" means Standard & Poor's Ratings Services, a division of The McGraw-
Hill Companies, Inc., and its successors.

     "Rating Agency" means each of Moody's and S&P; provided, that if either of
Moody's or S&P ceases to provide rating services to issuers or investors, we may
appoint a replacement for such Rating Agency that is reasonably acceptable to
the trustee under the Indenture.

     "Voting Stock" of any specified Person as of any date means the capital
stock of such Person that is at the time entitled to vote generally in the
election of the board of directors of such Person.

DISCHARGE, DEFEASANCE AND COVENANT DEFEASANCE

     The notes are not subject to defeasance or covenant defeasance.

REGISTRATION, TRANSFER AND EXCHANGE

     We appointed the Trustee as securities registrar for the purpose of
registering the notes and transfers and exchanges of the notes and, subject to
the terms of the Indenture, the notes may be presented for registration of
transfer and exchange at the offices of the trustee.


                                       S-9



                                  UNDERWRITING

     Under the terms and subject to the conditions contained in an underwriting
agreement dated the date of this prospectus supplement, the underwriters named
below, for whom Citigroup Global Markets Inc. and J.P. Morgan Securities Inc.
are acting as representatives, have severally agreed to purchase, and we have
agreed to sell to them, severally, the principal amount of notes indicated in
the following table:

<Table>
<Caption>
                                                                  PRINCIPAL AMOUNT OF
UNDERWRITER                                                              NOTES
- -----------                                                       -------------------
                                                               
Citigroup Global Markets Inc. ..................................      $
J.P. Morgan Securities Inc. ....................................
Banc of America Securities LLC..................................
BMO Capital Markets Corp. ......................................
Piper Jaffray & Co. ............................................
                                                                      -----------
  Total.........................................................                $
                                                                      ===========

</Table>


     The underwriters are offering the notes subject to their acceptance of the
notes from us and subject to prior sale. The underwriting agreement provides
that the obligations of the several underwriters to pay for and accept delivery
of the notes offered by this prospectus supplement are subject to the approval
of certain legal matters by their counsel and to certain other conditions. The
underwriters are obligated to take and pay for all of the notes offered by this
prospectus supplement if any are taken.

     Notes sold by the underwriters to the public will initially be offered at
the initial public offering price set forth on the cover page of this prospectus
supplement. Any notes sold by the underwriters to securities dealers may be sold
at a discount from the initial public offering price of up to      % of the
principal amount of the notes. Any such securities dealers may resell any notes
purchased from the underwriters to certain other brokers or dealers at a
discount from the initial public offering price of up to      % of the principal
amount of the notes. After the initial public offering of the notes, the
offering price and other selling terms may from time to time be varied by the
representative.

     The following table shows the underwriting discounts and commissions that
we are to pay to the underwriters in connection with this offering (expressed as
a percentage of the principal amount of the notes).

<Table>
<Caption>
                                                                       PAID BY
                                                                  GATX CORPORATION
                                                                  ----------------
                                                               
Per Note........................................................            %
</Table>


     In order to facilitate the offering of the notes, the underwriters may
engage in transactions that stabilize, maintain or otherwise affect the price of
the notes. Specifically, the underwriters may over-allot in connection with the
offering, creating a short position in the notes for their own account. In
addition, to cover overallotments or to stabilize the price of the notes, the
underwriters may bid for, and purchase, notes on the open market. Finally, the
underwriters may reclaim selling concessions allowed to an underwriter or a
dealer for distributing the notes in the offering, if the underwriters
repurchase previously distributed notes in transactions to cover syndicate short
positions, in stabilization transactions or otherwise. Any of these activities
may stabilize or maintain the market price of the notes above independent market
levels. The underwriters are not required to engage in these activities and may
end any of these activities at any time.

     The notes are a new issue of securities with no established trading market.
We have been advised by the underwriters that they intend to make a market in
the notes but are not obligated to do so and may discontinue market making at
any time without notice. We cannot assure you as to the liquidity of the trading
market for the notes.

     We estimate that our total expenses for this offering, not including the
underwriting discount, will be approximately $          .

     The underwriters have performed certain investment banking and advisory
services for us and our affiliates from time to time for which they have
received customary fees and expenses. The underwriters may,

                                      S-10



from time to time, engage in transactions with and perform services for us and
our affiliates in the ordinary course of their respective businesses. Certain
affiliates of the underwriters are lenders under our bank credit facilities.

     We have agreed to indemnify the underwriters against certain liabilities,
including liabilities under the Securities Act of 1933, or to contribute to
payments that the underwriters may be required to make because of any of those
liabilities.

SELLING RESTRICTIONS

     No action has been or will be taken in any jurisdiction (except in the
United States) that would permit a public offering of the notes, or the
possession, circulation or distribution of this prospectus supplement or the
accompanying prospectus or any other material relating to us or the notes, in
any jurisdiction where action for that purpose is required. Accordingly, the
notes offered by this prospectus supplement and the accompanying prospectus may
not be offered or sold, directly or indirectly, and this prospectus supplement,
the accompanying prospectus and any other offering material or advertisements in
connection with the notes may not be distributed or published, in or from any
country or jurisdiction except in compliance with any applicable rules and
regulations of any such country or jurisdiction.


                                      S-11



                                 LEGAL OPINIONS

     The validity of the notes will be passed upon on our behalf by Mayer Brown
LLP, Chicago, Illinois. The validity of the notes will be passed upon on behalf
of the underwriters by Winston & Strawn LLP, Chicago, Illinois.

                                     EXPERTS

     Our consolidated financial statements, appearing in our Current Report on
Form 8-K filed on August 9, 2007, and management's assessment of the
effectiveness of internal control over financial reporting, appearing in our
Annual Report on Form 10-K for the year ended December 31, 2006, have been
audited by Ernst & Young LLP, independent registered public accounting firm, as
set forth in their reports thereon included in our Current Report on Form 8-K
filed on August 9, 2007, and incorporated herein by reference. Such consolidated
financial statements and management's assessment are incorporated herein by
reference in reliance upon such reports given on the authority of such firm as
experts in accounting and auditing.


                                      S-12



PROSPECTUS


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


                                GATX CORPORATION

                                 DEBT SECURITIES

     We may offer and sell our debt securities from time to time in one or more
offerings. In this prospectus, we describe generally the terms of these debt
securities, which may consist of senior securities or subordinated securities.
We will describe the specific terms of the debt securities that we offer in a
supplement or supplements to this prospectus at the time of each offering. If
any offering involves underwriters, dealers or agents, we will describe our
arrangements with them in the prospectus supplement and if applicable, pricing
supplements, that relate to that offering.

     NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS
PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

                 The date of this prospectus is August 17, 2007



                                TABLE OF CONTENTS


<Table>
                                                                         
About This Prospectus....................................................     1
Disclosure Regarding Forward-Looking Statements..........................     1
GATX Corporation.........................................................     1
Ratio of Earnings to Fixed Charges.......................................     2
Use of Proceeds..........................................................     2
Description of Debt Securities...........................................     2
Concerning the Trustee...................................................    11
Plan of Distribution.....................................................    11
Legal Opinions...........................................................    12
Experts..................................................................    12
Where You Can Find More Information......................................    12
Documents Incorporated by Reference......................................    12
</Table>




                                        i



                              ABOUT THIS PROSPECTUS

     This prospectus is part of a registration statement that we filed with the
Securities and Exchange Commission using the shelf registration process. Under
this shelf process, the debt securities described in this prospectus may be sold
in one or more separate offerings. We provide information to you about these
securities in three documents that progressively provide more detail:

          1. This prospectus, which contains general information that may or may
     not apply to each offering of securities.

          2. The applicable prospectus supplement, which will contain more
     specific information than this prospectus and may also add, update or
     change information contained in this prospectus. To the extent information
     differs from this prospectus, you should rely on the different information
     in the applicable prospectus supplement.

          3. The pricing supplement, if applicable, will provide final details
     about a specific offering and the terms of the offered securities,
     including their price. To the extent information differs from this
     prospectus or the prospectus supplement, you should rely on the different
     information in the pricing supplement.

     You should read both this prospectus and any prospectus supplement or
pricing supplement together with any additional information described under the
heading "Where You Can Find More Information" below to learn more about us and
the securities offered.

     References in this prospectus to "GATX," "we," "us" and "our" refer to GATX
Corporation and its consolidated subsidiaries.

                 DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS

     This prospectus, any prospectus supplement delivered with this prospectus
and the documents we incorporate by reference may contain forward looking
statements within the meaning of Section 27A of the Securities Act of 1933 and
Section 21E of the Securities Exchange Act of 1934. These statements are
identified by such words as "anticipate," "believe," "estimate," "expect,"
"intend," "predict," or "project" and similar expressions. This information may
involve risks and uncertainties that could cause actual results to differ
materially from the forward-looking statements. Although we believe that the
expectations reflected in these forward-looking statements are based on
reasonable assumptions, these statements are subject to risks and uncertainties
that could cause actual results to differ materially from those projected. Many
of these risks and uncertainties may be described with particularity in the
applicable prospectus supplement or the documents incorporated by reference in
this prospectus.

     We undertake no obligation to update or revise our forward-looking
statements, whether as a result of new information, future events or otherwise.
In light of these risks, uncertainties and assumptions, the forward-looking
events discussed herein might not occur.

                                GATX CORPORATION

     GATX Corporation ("GATX" or the "Company") leases, manages, operates, and
invests in long-lived, widely used assets in the rail, marine and industrial
equipment markets. We are headquartered in Chicago, Illinois and provide our
services primarily through three operating segments: Rail, Specialty and
American Steamship Company ("ASC").

     Rail is principally engaged in leasing tank and freight railcars and
locomotives. Rail's railcar leasing customers are comprised largely of shippers
of chemical, petroleum, and food products, as well as railroads. Rail primarily
provides railcars pursuant to full-service leases under which it maintains the
railcars, pays ad valorem taxes, and provides other ancillary services. Rail
also offers net leases for railcars and most of its locomotives, in which case
the lessee is responsible for maintenance, insurance and taxes. In addition,
Rail manages railcars for third party owners for which it earns a fee. Rail
operates a network of major service centers across North America that perform
significant repair and regulatory compliance work on its railcars. Rail's North
American operation also includes its locomotive leasing business, which consists
of the purchase, reconditioning and leasing of four axle, medium

                                        1



horsepower locomotives. In Europe, Rail engages in leasing railcars through its
German, Austrian and Polish wholly owned subsidiaries. Rail operates in the home
countries of its subsidiaries and leases railcars to customers in these
countries as well as most other countries in Western and Central Europe. Rail
also operates two repair facilities in Europe that perform significant repairs
and regulatory compliance for owned railcars.

     Specialty manages a portfolio consisting primarily of leases, affiliate
investments, loans and interests in residual values involving a variety of
underlying asset types, including marine vessels, aircraft, rail, industrial and
other equipment. The portfolio provides recurring lease and interest income and
uneven periodic income primarily related to the remarketing of assets. Specialty
also provides equipment residual value guarantees, which enable it to share in
any asset value in excess of the guaranteed amount. Specialty further leverages
its equipment knowledge by managing portfolios of assets for third parties. The
majority of these managed assets are in markets in which we have a high level of
expertise. Specialty generates fee income through portfolio administration and
asset remarketing of these managed assets.

     ASC operates a fleet of self-unloading marine vessels on the Great Lakes
and is exclusively engaged in the waterborne transportation of dry bulk
commodities. ASC's customers are composed primarily of consumers of iron ore,
western and eastern coal, and metallurgical limestone and limestone aggregates.

GENERAL

     We are a New York corporation. Our principal offices are located at 500
West Monroe Street, Chicago, Illinois 60661-3676. Our telephone number is (312)
621-6200.

                       RATIO OF EARNINGS TO FIXED CHARGES

     The following table sets forth our ratio of earnings to fixed charges for
each of the periods indicated.

<Table>
<Caption>
                                           SIX MONTHS ENDED
                                         -------------------        YEAR ENDED DECEMBER 31,
                                         JUNE 30,   JUNE 30,   --------------------------------
                                           2007       2006     2006   2005   2004   2003   2002
                                         --------   --------   ----   ----   ----   ----   ----
                                                                      
Ratio of earnings to fixed charges(a)..    2.03x      1.79x    1.81x  1.63x  1.83x  1.22x  1.13x
</Table>


- --------

(a)    The ratio of earnings to fixed charges represents the number of times
       "fixed charges" are covered by "earnings". "Fixed charges" consist of
       interest on outstanding debt and amortization of debt discount and
       expense, adjusted for capitalized interest and the interest portion of
       operating lease expense. "Earnings" consist of income from continuing
       operations before income taxes and fixed charges, less share of
       affiliates' earnings, net of distributions received.

                                 USE OF PROCEEDS

     Unless otherwise indicated in the applicable prospectus supplement and
pricing supplement, if any, we will use the net proceeds from the sale of the
debt securities offered by this prospectus for general corporate purposes.

                         DESCRIPTION OF DEBT SECURITIES

     This section describes the general terms that will apply to any debt
securities that we may offer in the future, to which a future prospectus
supplement and pricing supplement, if any, may relate. At the time that we offer
debt securities, we will describe in the prospectus supplement and pricing
supplement, if any, that relates to that offering (1) the specific terms of the
debt securities and (2) the extent to which the general terms described in this
section apply to those debt securities.

     We expect to issue debt securities consisting of senior securities and
subordinated securities. The senior securities are to be issued under an
indenture between GATX and U.S. Bank National Association, as trustee. The
subordinated securities are to be issued under a separate indenture between GATX
and U.S. Bank National Association, as trustee. Forms of the indentures for the
senior securities and the subordinated securities are included as exhibits to
the registration statement to which this prospectus forms a part. In the
discussion that follows, we

                                        2



summarize particular provisions of the indentures. Our discussion of indenture
provisions is not complete. You should read the indentures for a more complete
understanding of the provisions we describe.

     The aggregate principal amount of debt securities that we may issue under
each of the indentures is unlimited.

GENERAL

     The indentures provide that debt securities in an unlimited amount may be
issued thereunder from time to time in one or more series. The senior securities
will rank equally and ratably with the other senior indebtedness of GATX. The
subordinated securities will be subordinated and junior in right of payment to
certain indebtedness of GATX to the extent set forth in the applicable
prospectus supplement.

     Each prospectus supplement and pricing supplement, if any, relating to a
particular offering of debt securities will describe the specific terms of debt
securities. Those specific terms will include the following:

     - the title of the debt securities;

     - any limit on the aggregate principal amount of the debt securities;

     - whether any of the debt securities are to be issuable initially in
       temporary global form and whether any of the debt securities are to be
       issuable in permanent global form;

     - the date or dates on which the debt securities will mature;

     - the rate or rates at which the debt securities will bear interest, if
       any, or the formula pursuant to which such rate or rates shall be
       determined, and the date or dates from which any such interest will
       accrue;

     - the payment dates on which interest, if any, on the debt securities will
       be payable, and the extent to which, or the manner in which, any interest
       payable on a temporary global debt security on an interest payment date
       will be paid;

     - any mandatory or optional sinking fund or analogous provisions;

     - each office or agency where, subject to the terms of the indenture, the
       principal of and any premium and interest on the debt securities will be
       payable and each office or agency where, subject to the terms of the
       indenture, the debt securities may be presented for registration of
       transfer or exchange;

     - the date, if any, after which and the price or prices at which the debt
       securities may be redeemed, in whole or in part at the option of GATX or
       the holder of debt securities, or according to mandatory redemption
       provisions, and the other detailed terms and provisions of any such
       optional or mandatory redemption provisions;

     - the denominations in which any debt securities will be issuable, if other
       than denominations of $1,000;

     - any index used to determine the amount of payments of principal of and
       any premium and interest on the debt securities;

     - the portion of the principal amount of the debt securities, if other than
       the principal amount, payable upon acceleration of maturity;

     - the person who shall be the security registrar for the debt securities,
       if other than the trustee, the person who shall be the initial paying
       agent and the person who shall be the depositary;

     - the terms of subordination applicable to any series of subordinated
       securities; and

     - any other terms of the debt securities not inconsistent with the
       provisions of the indentures.

     Any such prospectus supplement and pricing supplement, if any, will also
describe any special provisions for the payment of additional amounts with
respect to the debt securities of such series.

     Except where specifically described in the applicable prospectus supplement
and pricing supplement, if any, the indentures do not contain any covenants
designed to protect holders of the debt securities against a reduction in

                                        3



the creditworthiness of GATX in the event of a highly leveraged transaction or
to prohibit other transactions which may adversely affect holders of the debt
securities.

     We may issue debt securities as original issue discount securities to be
sold at a substantial discount below their stated principal amounts. We will
describe in the relevant prospectus supplement and pricing supplement, if any,
any special United States federal income tax considerations that may apply to
debt securities issued at such an original issue discount. Special United States
tax considerations applicable to any debt securities that are denominated in a
currency other than United States dollars or that use an index to determine the
amount of payments of principal of and any premium and interest on the debt
securities will also be set forth in a prospectus supplement and pricing
supplement, if any.

BOOK ENTRY SYSTEM

     According to the indentures, so long as the depositary's nominee is the
registered owner of a global security, that nominee will be considered the sole
owner of the debt securities represented by the global security for all
purposes. Except as provided in the relevant prospectus supplement and pricing
supplement, if any, owners of beneficial interests in a global security will not
be entitled to have debt securities of the series represented by the global
security registered in their names, will not receive or be entitled to receive
physical delivery of debt securities of such series in definitive form and will
not be considered the owners or holders of the debt securities under the
indentures. Principal of, premium, if any, and interest on a global security
will be payable in the manner described in the relevant prospectus supplement
and pricing supplement, if any.

     Unless otherwise provided in the prospectus supplement, the global security
representing debt securities will be deposited with, or on behalf of, The
Depository Trust Company ("DTC"), or other successor depositary appointed by us
(DTC or such other depositary is referred to in this prospectus as the
"depositary") and registered in the name of the depositary or its nominee. The
global security will bear a legend regarding the restrictions on exchange and
registration of transfer referred to below and any other matters as may be
provided for in the indentures. Debt securities will not be issued in definitive
form unless the prospectus supplement states otherwise.

     No global security may be exchanged for registered debt securities, and no
transfer of a global security may be registered in the name of any person other
than the depositary or its nominee unless:

     - the depositary has notified us that it is unwilling or unable to continue
       as depositary or has ceased to be qualified to act as depositary as
       required by the indentures; or

     - there exist any other circumstances described in the applicable
       prospectus supplement. All debt securities issued in exchange for a
       global security or any portion of a global security will be registered in
       the names that the depositary directs.

     DTC has advised that:  it is a limited-purpose trust company organized
under the Banking Law of the State of New York, a member of the Federal Reserve
System, a "clearing corporation" within the meaning of the New York Uniform
Commercial Code and a "clearing agency" registered pursuant to the provisions of
Section 17A of the Securities Exchange Act of 1934. DTC holds securities that
its participants deposit with DTC. DTC also facilitates the settlement among
participants of securities transactions, such as transfers and pledges, in
deposited securities through electronic computerized book-entry changes in
participants' accounts. This eliminates the need for physical movement of
securities certificates. Direct participants include securities brokers and
dealers, banks, trust companies, clearing corporations and certain other
organizations, some of whom (and/or their representatives) own the depositary.
Access to DTC's book-entry system is also available to others, such as banks,
brokers, dealers and trust companies that clear through or maintain a custodial
relationship with a direct participant, either directly or indirectly. The rules
applicable to DTC and its participants are on file with the SEC.

     Clearstream, Luxembourg advises that it is incorporated under the laws of
Luxembourg as a professional depositary. Clearstream, Luxembourg holds
securities for its participating organizations ("Clearstream Participants") and
facilitates the clearance and settlement of securities transactions between
Clearstream Participants through electronic book-entry changes in accounts of
Clearstream Participants, thereby eliminating the need for physical movement of
certificates. Clearstream, Luxembourg provides to Clearstream Participants,
among other things, services for safekeeping, administration, clearance and
settlement of internationally traded securities and

                                        4



securities lending and borrowing. Clearstream, Luxembourg interfaces with
domestic markets in several countries. As a professional depositary,
Clearstream, Luxembourg is subject to regulation by the Luxembourg Commission
for the Supervision of the Financial Sector (Commission de Surveillance du
Secteur Financier). Clearstream Participants are recognized financial
institutions around the world, including underwriters, securities brokers and
dealers, banks, trust companies, clearing corporations and certain other
organizations and may include the underwriters. Indirect access to Clearstream,
Luxembourg is also available to others, such as banks, brokers, dealers and
trust companies that clear through or maintain a custodial relationship with a
Clearstream Participant, either directly or indirectly.

     Distributions with respect to interests in the debt securities held
beneficially through Clearstream, Luxembourg will be credited to cash accounts
of Clearstream Participants in accordance with its rules and procedures, to the
extent received by Clearstream, Luxembourg.

     Euroclear advises that it was created in 1968 to hold securities for
participants of Euroclear ("Euroclear Participants") and to clear and settle
transactions between Euroclear Participants through simultaneous electronic
book-entry delivery against payment, thereby eliminating the need for physical
movement of certificates and any risk from lack of simultaneous transfers of
securities and cash. Euroclear includes various other services, including
securities lending and borrowing and interfaces with domestic markets in several
countries. Euroclear is operated by Euroclear Bank S.A./N.V (the "Euroclear
Operator"). All operations are conducted by the Euroclear Operator, and all
Euroclear securities clearance accounts and Euroclear cash accounts are accounts
with the Euroclear Operator. Euroclear Participants include banks (including
central banks), securities brokers and dealers and other professional financial
intermediaries and may include the underwriters. Indirect access to Euroclear is
also available to other firms that clear through or maintain a custodial
relationship with a Euroclear Participant, either directly or indirectly.

     Securities clearance accounts and cash accounts with the Euroclear Operator
are governed by the Terms and Conditions Governing Use of Euroclear and the
related Operating Procedures of the Euroclear System, and applicable Belgian law
(collectively, the "Terms and Conditions"). The Terms and Conditions govern
transfers of securities and cash within the Euroclear System, withdrawals of
securities and cash from the Euroclear System, and receipts of payments with
respect to securities in the Euroclear System. All securities in the Euroclear
System are held on a fungible basis without attribution of specific certificates
to specific securities clearance accounts. The Euroclear Operator acts under the
Terms and Conditions only on behalf of Euroclear Participants, and has no
records of or relationship with persons holding through Euroclear Participants.

     Distributions with respect to the debt securities held beneficially through
the Euroclear System will be credited to the cash accounts of Euroclear
Participants in accordance with the Terms and Conditions, to the extent received
by the Euroclear System.

     When we issue debt securities represented by a global security, purchases
of debt securities under the DTC system must be made by or through direct
participants, which will receive a credit for the debt securities on DTC's
records. The ownership interest of each actual purchaser of each debt security
is in turn to be recorded on the direct and indirect participants' records.
Beneficial owners will not receive written confirmation from DTC of their
purchase, but beneficial owners are expected to receive written confirmations
providing details of the transaction, as well as periodic statements of their
holdings, from the direct or indirect participant through which the beneficial
owner entered into the transaction. Transfers of ownership interests in the debt
securities are to be accomplished by entries made on the books of participants
acting on behalf of beneficial owners. Beneficial owners will not receive
certificates representing their ownership interests in debt securities, except
when use of the book-entry system for the debt securities is discontinued. The
laws of some states require that certain purchasers of securities take physical
delivery of the securities in definitive form. These laws may impair the ability
to transfer beneficial interests in a global security.

     When the depositary, or its nominee, is the registered owner of the global
security, it will be considered the sole owner or holder of the debt securities
represented by the global security for all purposes under the indentures. Except
as described above, beneficial owners:

     - will not be entitled to have debt securities represented by the global
       security registered in their names;


                                        5



     - will not receive or be entitled to receive physical delivery of debt
       securities in definitive form; and

     - will not be considered the owners or holders of the global security or
       any debt securities represented by the global security for any purpose
       under the indentures.

     To facilitate subsequent transfers, all debt securities deposited by
participants with DTC are registered in the name of DTC's partnership nominee,
Cede & Co. The deposit of debt securities with DTC and their registration in the
name of Cede & Co. effect no change in beneficial ownership. DTC has no
knowledge of the actual beneficial owners of the debt securities; DTC's records
reflect only the identity of the direct participants to whose accounts such debt
securities are credited, which may or may not be the beneficial owners. The
participants will remain responsible for keeping account of their holdings on
behalf of their customers. Conveyance of notices and other communications by DTC
to direct participants, by direct participants to indirect participants, and by
direct participants and indirect participants to beneficial owners will be
governed by arrangements among them, subject to any statutory or regulatory
requirements as may be in effect from time to time.

     Neither DTC nor Cede & Co. will consent or vote with respect to debt
securities. Under its usual procedures, DTC mails an omnibus proxy to us as soon
as possible after the record date. The omnibus proxy assigns Cede & Co.'s
consenting or voting rights to those direct participants to whose accounts the
debt securities are credited on the record date (identified in a listing
attached to the omnibus proxy).

     Payments of any principal of and interest on the debt securities
represented by the global security registered in the name of the depositary or
its nominee will be made by us through the Trustee or a paying agent, which may
also be the Trustee, to the depositary or its nominee as the registered owner of
the global security. Neither we, the Trustee, nor the paying agent will have any
responsibility or liability for any aspect of the records relating to or
payments made on account of beneficial ownership interests of the global
security or for maintaining, supervising or reviewing any records relating to
such beneficial ownership interests.

     We have been advised that DTC will credit direct participants' accounts,
upon DTC's receipt of funds and corresponding detail information from us or the
Trustee, on the payment date in accordance with their respective holdings shown
on DTC's records. Payments by participants to beneficial owners will be governed
by standing instructions and customary practices, as in the case with securities
held for the accounts of customers in bearer form or registered in "street
name," and will be the responsibility of the participant and not of DTC, the
paying agent or us, subject to any statutory or regulatory requirements as may
be in effect from time to time. Payment of principal and interest to DTC is the
responsibility of GATX or the paying agent, disbursement of those payments to
direct participants shall be the responsibility of DTC and disbursement of the
payments to the beneficial owners shall be the responsibility of direct and
indirect participants.

     The information in this section concerning the depositary and the
depositary's book-entry system has been obtained from sources that we believe to
be reliable, but we take no responsibility for the accuracy of this information.

GLOBAL CLEARANCE AND SETTLEMENT PROCEDURES

     Initial settlement for the debt securities will be made in immediately
available funds. Secondary market trading between DTC Participants will occur in
the ordinary way in accordance with DTC rules and will be settled in immediately
available funds using DTC's Same-Day Funds Settlement System. Secondary market
trading between Clearstream Participants and/or Euroclear Participants will
occur in the ordinary way in accordance with the applicable rules and operating
procedures of Clearstream, Luxembourg and the Euroclear System, as applicable.

     Cross-market transfers between persons holding directly or indirectly
through DTC on the one hand, and directly or indirectly through Clearstream
Participants or Euroclear Participants, on the other, will be effected through
DTC in accordance with DTC rules of the relevant European international clearing
system; however, such cross-market transactions will require delivery of
instructions to the relevant European international clearing system by the
counterparty in such system in accordance with its rules and procedures and
within its established deadlines (European time). The relevant European
international clearing system will, if the transaction meets its settlement
requirements, effect final settlement on its behalf by delivering or receiving
securities in DTC, and making or receiving payment in accordance with normal
procedures for same-day funds settlement applicable to

                                        6



DTC. Clearstream Participants and Euroclear Participants will be required to
deliver instructions directly to Clearstream, Luxembourg or the Euroclear
System, as the case may be.

     Because of time-zone differences, credits of debt securities received in
Clearstream, Luxembourg or the Euroclear System as a result of a transaction
with a DTC Participant will be made during subsequent securities settlement
processing and dated the business day following the DTC settlement date. Such
credits or any transactions in such debt securities settled during such
processing will be reported to the relevant Euroclear Participant or Clearstream
Participant on such business day. Cash received in Clearstream, Luxembourg or
the Euroclear System as a result of sales of the debt securities by or through a
Clearstream Participant or a Euroclear Participant to a DTC Participant will be
received with value on the DTC settlement date but will be available in the
relevant Clearstream, Luxembourg or the Euroclear System cash account only as of
the business day following settlement in DTC.

     Although DTC, Clearstream, Luxembourg and the Euroclear System have agreed
to the foregoing procedures in order to facilitate transfers of debt securities
among participants of DTC, Clearstream, Luxembourg and the Euroclear System,
they are under no obligation to perform or continue to perform such procedures
and such procedures may be discontinued or changed at any time.

FORM, EXCHANGE AND TRANSFER

     We will issue the debt securities of each series only in registered form,
without coupons, and, unless otherwise specified in the applicable prospectus
supplement, only in denominations of $1,000 and integral multiples thereof.

     Holders may, at their option, but subject to the terms of the indentures
and the limitations that apply to global securities, exchange their debt
securities for other debt securities of the same series containing identical
terms and provisions, in any authorized denomination and of a like tenor and
aggregate principal amount.

     Subject to the terms of the indentures and the limitations that apply to
global securities, holders may exchange debt securities as provided above. No
service charge applies for any registration of transfer or exchange of debt
securities, but the holder may have to pay any tax or other governmental charge
associated with registration of transfer or exchange. We have appointed the
Trustee as security registrar. Any transfer agent (in addition to the security
registrar) initially designated by us for any debt securities will be named in
the applicable prospectus supplement. We may at any time designate additional
transfer agents or cancel the designation of any transfer agent or approve a
change in the office through which any transfer agent acts. However, we will be
required to maintain a transfer agent in each place of payment for the debt
securities of each series.

     If the debt securities are to be partially redeemed, we will not be
required to:

     - issue or register the transfer of or exchange any debt security during a
       period beginning 15 days before the day of the selection for redemption
       of the debt securities of the applicable series and ending on the close
       of business on the day of such selection; or

     - register the transfer of or exchange any debt security selected for
       redemption, in whole or in part, except the unredeemed portion of any
       debt security being redeemed in part.

PAYMENT AND PAYING AGENTS

     We will pay interest on a debt security on any interest payment date to the
registered holder of the debt security as of the close of business on the
regular record date for payment of interest. If the debt securities do not
remain in book entry form, the record date for each interest payment date will
be the close of business on the fifteenth calendar day immediately preceding the
applicable interest payment date. If we default in paying interest on a debt
security, we will pay such interest either:

     - on a special record date between 10 and 15 days before the payment; or

     - in any other lawful manner of payment that is consistent with the
       requirements of any securities exchange on which the debt securities may
       be listed for trading.


                                        7



     We will pay the principal of and any premium and interest on the debt
securities at the office of the paying agent or paying agents that we designate.
We may pay interest by check mailed to the address of the person entitled to the
payment as the address appears in the security register. We have designated the
corporate trust office of the Trustee as our sole paying agent for payments on
the debt securities. Any other paying agents initially designated by us for the
debt securities will be named in the applicable prospectus supplement. We may at
any time designate additional paying agents, rescind the designation of any
paying agent or approve a change in the office through which any paying agent
acts.

     Any money paid by us to a paying agent for the payment of the principal of
or any premium or interest on any debt security which remains unclaimed at the
end of two years after the principal, premium or interest has become due and
payable may be repaid to us at our request.

SUBORDINATION

     We may issue subordinated securities from time to time in one or more
series under the subordinated indenture. Our subordinated securities will be
subordinated and junior in right of payment to certain other indebtedness of
GATX to the extent set forth in the applicable prospectus supplement and pricing
supplement, if any.

CERTAIN COVENANTS OF GATX WITH RESPECT TO SENIOR SECURITIES

     In this section we describe the principal covenants that will apply to the
senior securities unless otherwise indicated in the applicable prospectus
supplement and pricing supplement, if any.

     Limitation on Liens.  The senior securities offered hereby are not secured
by mortgage, pledge or other lien. We have covenanted that neither we nor any
Restricted Subsidiary (which the indenture relating to the senior securities
defines as any subsidiary which is a consolidated subsidiary, in accordance with
generally accepted accounting principles) will subject any of our property,
tangible or intangible, real or personal, to any lien unless the senior
securities are secured equally and ratably with other indebtedness thereby
secured. Specifically excluded from this covenant are liens existing on the date
of the indenture, as well as certain other liens, and the extension, renewal or
replacement of those liens including without limitation:

          (a) Liens on any property provided that the creditor has no recourse
     against GATX or any Restricted Subsidiary except recourse to such property
     or proceeds of any sale or lease of such property;

          (b) Liens on property existing at the time of acquisition (including
     acquisition through merger or consolidation) or given in connection with
     financing the purchase price or cost of construction or improvement of
     property so long as the financing is completed within 180 days of the
     acquisition (or 18 months in the case of rail equipment, marine equipment,
     transportation-related containers and certain information technology
     assets);

          (c) Liens securing certain intercompany indebtedness;

          (d) A banker's lien or right of offset;

          (e) Liens arising under the Employee Retirement Income Security Act of
     1974, as amended, to secure any contingent liability of GATX;

          (f) Liens on sublease interests held by GATX if those liens are in
     favor of the person leasing the property subject to the sublease to GATX;

          (g) Various specified governmental liens and deposits;

          (h) Various other liens not incurred in connection with the borrowing
     of money (including purchase money indebtedness) or the obtaining of
     advances or credit;

          (i) Liens incurred in connection with securing performance of letters
     of credit, bids, tenders, appeal and performance bonds not incurred in
     connection with the borrowing of money or obtaining of advances or payment
     of the deferred purchase price of property; and


                                        8



          (j) Other liens not permitted by any of the preceding clauses on
     property, provided no such lien shall be incurred pursuant to clause (j) if
     the aggregate amount of indebtedness secured by liens incurred pursuant to
     clause (j) subsequent to the date of the indenture, including the lien
     proposed to be incurred, would exceed 20% of Net Tangible Assets (which the
     indenture relating to the senior securities defines as the total assets of
     GATX less (x) current liabilities and (y) intangible assets).

SATISFACTION AND DISCHARGE

     We may be discharged from our obligations on the debt securities of any
series that have matured or will mature or be redeemed within one year if we
deposit with the trustee enough cash or U.S. government obligations to pay all
the principal, interest and any premium due to the stated maturity date or
redemption date of debt securities.

MERGER AND CONSOLIDATION

     Each indenture provides that we may not consolidate or merge with or into
any other corporation or sell or convey all or substantially all of our assets
to any other corporation, unless we are the continuing corporation or successor
corporation, or the successor or transferee corporation is a corporation
organized and existing under the laws of the United States or any state thereof
or the District of Columbia and expressly assumes all of our obligations under
the applicable indenture and, immediately after giving effect to the
consolidation, merger, sale or conveyance, we or the successor or transferee
corporation will not be in default of the performance of any covenant or
condition in the indenture.

MODIFICATION AND WAIVER

     The indentures provide that we and the trustee may modify and amend the
indentures with the consent of the holders of a majority in principal amount of
the outstanding debt securities of each series affected by the modification or
amendment, provided that no such modification or amendment may, without the
consent of the holder of each outstanding debt security affected by the
modification or amendment:

     - Change the stated maturity of the principal of, or any installment of
       interest on or any additional amounts payable with respect to, any debt
       security or change the redemption price;

     - Reduce the principal amount of, or interest on, any debt security or
       reduce the amount of principal which could be declared due and payable
       prior to the stated maturity;

     - Change the place or currency of any payment of principal or interest on
       any debt security;

     - Impair the right to institute suit for the enforcement of any payment on
       or with respect to any debt security;

     - Reduce the percentage in principal amount of the outstanding debt
       securities of any series, the consent of whose holders is required to
       modify or amend each indenture; or

     - Modify the foregoing requirements or reduce the percentage of outstanding
       debt securities necessary to waive any past default to less than a
       majority.

Except with respect to certain fundamental provisions, the holders of at least a
majority in principal amount of outstanding debt securities of any series may,
with respect to such series, waive past defaults under each indenture.

EVENTS OF DEFAULT, WAIVER AND NOTICE

     An event of default with respect to any debt security of any series is
defined in each indenture as being:

     - Default in payment of any interest on or any additional amounts payable
       in respect of any debt security of that series which remains uncured for
       a period of 30 days;

     - Default in payment of principal (and premium, if any) on the debt
       securities of that series when due either at maturity, upon optional or
       mandatory redemption, as a sinking fund installment, by declaration or
       otherwise;

     - Our default in the performance or breach of any other covenant or
       agreement in respect of the debt securities of such series in each
       indenture which shall not have been remedied for a period of 90 days
       after notice;


                                        9



     - Certain events regarding our bankruptcy, insolvency and reorganization;
       and

     - Any other event of default established for the debt securities of such
       series set forth in the applicable prospectus supplement and pricing
       supplement, if any.

Each indenture provides that the trustee may withhold notice to the holders of
the debt securities of any default with respect to any series of debt securities
(except in payment of principal of, or interest on, the debt securities) if the
trustee considers it in the interest of the holders of the debt securities of
such series to do so.

     Each indenture provides also that:

     - If an event of default due to the default in payment of principal of, or
       interest on, any series of debt securities, or because of our default in
       the performance or breach of any other covenant or agreement applicable
       to the debt securities of such series but not applicable to all
       outstanding debt securities, shall have occurred and be continuing,
       either the trustee or the holders of not less than 25% in principal
       amount of the outstanding debt securities of such series then may declare
       the principal of all debt securities of that series, or such lesser
       amount as may be provided for in the debt securities of that series, and
       interest accrued thereon, to be due and payable immediately; and

     - If the event of default resulting from our default in the performance of
       any other of the covenants or agreements in each indenture applicable to
       all outstanding debt securities under such indenture or certain events of
       bankruptcy, insolvency and reorganization shall have occurred and be
       continuing, either the trustee or the holders of not less than 25% in
       principal amount of all outstanding debt securities (treated as one
       class) may declare the principal of all debt securities, or such lesser
       amount as may be provided for in such securities, and interest accrued
       thereon, to be due and payable immediately,

but upon certain conditions such declarations may be annulled and past defaults
may be waived (except a continuing default in payment of principal of, or
premium or interest on, the debt securities) by the holders of a majority in
principal amount of the outstanding debt securities of such series (or of all
series, as the case may be).

     The holders of a majority in principal amount of the outstanding debt
securities of any series shall have the right to direct the time, method and
place of conducting any proceeding for any remedy available to the trustee or
exercising any trust or power conferred on the trustee with respect to debt
securities of such series provided that such direction shall not be in conflict
with any rule of law or the applicable indenture and shall not be unduly
prejudicial to the holders not taking part in such direction. The trustee may
also take any other action it deems proper which is consistent with the holders'
direction. If an event of default or other default occurs and is continuing
after any applicable notice and/or cure period, then the trustee may in its
discretion (and subject to the rights of the holders to control remedies as
described above and certain other conditions specified in the indentures) bring
such judicial proceedings as the trustee shall deem appropriate or proper.

     The indentures provide that no holder of any debt security will have any
right to institute any proceeding, judicial or otherwise, with respect to the
indentures for the appointment of a receiver or trustee for any other remedy
thereunder unless:

     - that holder has previously given the trustee written notice of a
       continuing event of default;

     - the holders of not less than 25% in principal amount of the outstanding
       debt securities of any series have made written request to the trustee to
       institute proceedings in respect of that event of default and have
       offered the trustee reasonable indemnity against costs and liabilities
       incurred in complying with such request; and

     - for 60 days after receipt of such notice, request and offer of indemnity,
       the trustee has failed to institute any such proceeding and no direction
       inconsistent with such request has been given to the Trustee during such
       60-day period by the holders of a majority in principal amount of
       outstanding debt securities.

     Furthermore, no holder will be entitled to institute any such action if and
to the extent that such action would disturb or prejudice the rights of other
holders.

     However, each holder has an absolute and unconditional right to receive
payment when due and to bring a suit to enforce that right. We are required to
furnish to the trustee under each indenture annually a statement as to

                                       10



performance or fulfillment of its obligations under the applicable indenture and
as to any default in such performance or fulfillment.

     Notices to holders of the debt securities will be given by mail to the
address of the holders as they may appear in the security register.

     We, and any agent of us or the trustee, will treat any person or entity in
whose name securities are registered as the absolute owner of those debt
securities (whether or not the debt securities may be overdue) for the purpose
of making payments and for all other purpose respective of notice to the
contrary.

                             CONCERNING THE TRUSTEE

     U.S. Bank National Association is the trustee under the indenture for our
outstanding senior debt securities, as well as certain of our equipment trust
agreements. We maintain banking relationships in the ordinary course of business
with U.S. Bank National Association and its affiliates.

                              PLAN OF DISTRIBUTION

     We may sell the debt securities directly to purchasers, through agents,
underwriters, or dealers, or through a combination of any of these methods of
sale.

     We may distribute the debt securities from time to time in one or more
transactions at:

     - fixed prices (which may be changed from time to time);

     - market prices prevailing at the time of sale;

     - prices related to the prevailing market prices; or

     - negotiated prices.

Each prospectus supplement and pricing supplement, if any, will describe the
method of distribution of the debt securities offered by that prospectus
supplement and pricing supplement, if any.

     We may designate agents to solicit offers to purchase the debt securities
from time to time. The relevant prospectus supplement will name the agents and
any commissions we pay them. Unless otherwise indicated in the prospectus
supplement, any agent will be acting on a reasonable best efforts basis for the
period of its appointment.

     If we use any underwriters for the sale of any of the debt securities, we
will enter into an underwriting agreement with them at the time of sale, and the
names of the underwriters and the terms of the transaction, including
commissions, discounts and other compensation of the underwriters and dealers,
if any, will be set forth in the prospectus supplement that those underwriters
will use to resell the debt securities.

     If we use dealers for the sale of the debt securities, we will sell the
debt securities to those dealers, as principal. The dealers may then resell the
debt securities to the public at varying prices to be determined by them at the
time of resale.

     In connection with the sale of the debt securities, underwriters, dealers
or agents may receive compensation from us or from purchasers of the debt
securities for whom they may act as agents, in the form of discounts,
concessions or commissions. The underwriters, dealers or agents that participate
in the distribution of the debt securities may be deemed to be underwriters
under the Securities Act of 1933 and any discounts or commissions received by
them and any profit on the resale of the debt securities received by them may be
deemed to be underwriting discounts and commissions thereunder. Any such
underwriter, dealer or agent will be identified and any such compensation
received from us will be described in the prospectus supplement and pricing
supplement, if any. Any initial public offering price and any discounts or
concessions allowed or reallowed or paid to dealers may be changed from time to
time.

     We may indemnify agents, underwriters and dealers against certain
liabilities, including liabilities under the Securities Act, or to contribute
with respect to payments they may be required to make.


                                       11



     Some of the underwriters, dealers or agents and their respective affiliates
may be customers of, engage in transactions with and perform services for us or
our affiliates in the ordinary course of business.

                                 LEGAL OPINIONS

     Unless otherwise stated in a prospectus supplement, Mayer, Brown, Rowe &
Maw LLP, Chicago, Illinois, will pass on the validity of the debt securities
offered by this prospectus.

                                     EXPERTS

     Our consolidated financial statements, appearing in our Current Report on
Form 8-K filed on August 9, 2007, and management's assessment of the
effectiveness of internal control over financial reporting, appearing in our
Annual Report on Form 10-K for the year ended December 31, 2006, have been
audited by Ernst & Young LLP, independent registered public accounting firm, as
set forth in their reports thereon included in our Current Report on Form 8-K
filed on August 9, 2007, and incorporated herein by reference. Such consolidated
financial statements and management's assessment are incorporated herein by
reference in reliance upon such reports given on the authority of such firm as
experts in accounting and auditing.

                       WHERE YOU CAN FIND MORE INFORMATION

     We file annual, quarterly and current reports and proxy statements and
other information with the Securities and Exchange Commission. Our SEC filings
are available over the internet at the SEC's web site at http://www.sec.gov. You
may also read and copy any document we file with the SEC at its public reference
facility:

                              Public Reference Room
                               100 F Street, N.E.
                                    Room 1580
                             Washington, D.C. 20549

     You may also obtain copies of the documents at prescribed rates by writing
to the Public Reference Section of the SEC at 100 F. Street, N.E., Room 1580,
Washington, D.C. 20549. Please call 1-800-SEC-0330 for further information on
the operations of the public reference facility and copying charges. Our SEC
filings are also available at the offices of the New York Stock Exchange, 20
Broad Street, New York, New York 10005 and the offices of the Chicago Stock
Exchange at 120 South LaSalle Street, Chicago, Illinois 60603.

                       DOCUMENTS INCORPORATED BY REFERENCE

     The SEC allows us to incorporate by reference information into this
prospectus. This means that we can disclose important information to you by
referring you to another document filed separately with the SEC. The information
incorporated by reference is considered to be part of this prospectus, except
for any information that is superseded by information that is included directly
in this document. This prospectus incorporates by reference the documents listed
below:

     - Annual Report on Form 10-K for the fiscal year ended December 31, 2006;

     - Quarterly Reports on Form 10-Q for the fiscal quarters ended March 31,
       2007 and June 30, 2007;

     - Current Reports on Form 8-K filed on January 3, 2007, April 27, 2007, May
       11, 2007, May 16, 2007, July 30, 2007 and August 9, 2007.

     We also incorporate by reference all documents we file with the SEC
pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of
1934 after the date of this prospectus and prior to the termination of this
offering. Our subsequent filings with the SEC will automatically update and
supersede information in this prospectus.


                                       12



     Statements made in this prospectus or in any document incorporated by
reference in this prospectus as to the contents of any contract or other
document referred to herein or therein are not necessarily complete, and in each
instance reference is made to the copy of such contract or other document filed
as an exhibit to the documents incorporated by reference, each such statement
being qualified in all material respects by such reference.

     You may request a copy of any filings referred to above, at no cost,
excluding any exhibits to those filings unless the exhibit is specifically
incorporated by reference in those filings, by writing or telephoning us at the
following address and telephone number:

     Lisa M. Ibarra
     Assistant Secretary
     GATX Corporation
     500 West Monroe Street
     Chicago, Illinois 60661-3676
     (312) 621-6200


                                       13



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                                        $

                                GATX CORPORATION

                                  % SENIOR NOTES DUE

                                     -------

                              PROSPECTUS SUPPLEMENT

                                          , 2008

                                     -------


                                      CITI
                                    JPMORGAN
                         BANC OF AMERICA SECURITIES LLC
                               BMO CAPITAL MARKETS
                                  PIPER JAFFRAY

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