UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 11-K

þ ANNUAL REPORT PURSUANT TO SECTION 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2007

OR

o TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from ___to ___

Commission file number 1-2328

A. Full title of the plan and the address of the plan, if different from that of the issuer named below:

GATX CORPORATION SALARIED EMPLOYEES RETIREMENT SAVINGS PLAN

B. Name of the issuer of the securities held pursuant to the plan and the address of its principal executive office:

GATX Corporation

222 West Adams Street
Chicago, Illinois 60606-5314

GATX CORPORATION SALARIED EMPLOYEES RETIREMENT SAVINGS PLAN
INDEX TO FINANCIAL STATEMENTS AND SUPPLEMENTAL SCHEDULE

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM	3
FINANCIAL STATEMENTS:
Statements of Assets Available for Benefits	4
Statements of Changes in Assets Available for Benefits	5
NOTES TO FINANCIAL STATEMENTS	6
SUPPLEMENTAL SCHEDULE:
Schedule H, Line 4i — Schedule of Assets (Held at End of Year)	14
Other schedules required by Section 2520.103-10 of the Departments of Labor’s Rules and Regulations for Reporting and Disclosure under ERISA have been omitted because they are not applicable.
SIGNATURE	15
EXHIBIT INDEX	16
Consent of Independent Registered Public Accounting Firm

2

Report of Independent Registered Public Accounting Firm

Employee Benefits Committee
GATX Corporation

We have audited the accompanying statements of assets available for benefits of the GATX Corporation Salaried Employees Retirement Savings Plan (the Plan) as of December 31, 2007 and 2006, and the related statements of changes in assets available for benefits for the years then ended. These financial statements are the responsibility of the Plan’s management. Our responsibility is to express an opinion on these financial statements based on our audits.

We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. We were not engaged to perform an audit of the Plan’s internal control over financial reporting. Our audits included consideration of internal control over financial reporting as a basis for designing audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the Plan’s internal control over financial reporting. Accordingly, we express no such opinion. An audit also includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in all material respects, the assets available for benefits of the Plan at December 31, 2007 and 2006, and the changes in its assets available for benefits for the years then ended, in conformity with U.S. generally accepted accounting principles.

Our audits were performed for the purpose of forming an opinion on the financial statements taken as a whole. The accompanying supplemental schedule of assets (held at end of year) as of December 31, 2007, is presented for purposes of additional analysis and is not a required part of the financial statements, but is supplementary information required by the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. This supplemental schedule is the responsibility of the Plan’s management. This supplemental schedule has been subjected to the auditing procedures applied in our audits of the financial statements and, in our opinion, is fairly stated in all material respects in relation to the financial statements taken as a whole.

/s/ Ernst & Young LLP  

Ernst & Young LLP 

June 23, 2008
Chicago, Illinois

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EIN 36-1124040
Plan #002

GATX Corporation Salaried Employees Retirement Savings Plan

Statements of Assets Available for Benefits

	December 31
	2007		2006
Assets
Investments in mutual funds	$	77,174,827	$	89,217,435
Interest in Collective Trusts		37,178,039		27,276,315
Interest in Master Trust		28,379,594		37,823,797
Participant loans		1,564,874		1,676,958
Total investments		144,297,334		155,994,505
Employer contribution receivable		54,296		43,997
Assets available for benefits at fair value		144,351,630		156,038,502
Adjustment from fair value to contract value for interest in Collective Trusts relating to fully benefit-responsive investment contracts		193,597		327,046
Assets available for benefits	$	144,545,227	$	156,365,548

See notes to financial statements.

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EIN 36-1124040
Plan #002

GATX Corporation Salaried Employees Retirement Savings Plan

Statements of Changes in Assets Available for Benefits

	Year Ended December 31
	2007			2006
Additions
Investment income:
Net investment gain from mutual funds	$	4,258,241		$	5,691,616
Net investment loss from Collective Trusts		(947,350	)		—
Net investment (loss) gain from Master Trust		(3,812,801	)		8,061,836
Interest and dividend income		4,410,024			6,218,835
		3,908,114			19,972,287
Contributions from GATX		1,340,302			1,445,064
Participant salary deferrals		4,775,370			5,114,895
Rollover contributions		511,995			441,887
Transfer from GATX Hourly Employees Retirement Savings Plan		53,718			138,151
		10,589,499			27,112,284
Deductions
Benefit payments		(22,398,910	)		(15,733,280	)
Administrative fee		(10,910	)		(6,328	)
		(22,409,820	)		(15,739,608	)
Net (decrease) increase in plan assets		(11,820,321	)		11,372,676
Assets available for benefits:
Beginning of year		156,365,548			144,992,872
End of year	$	144,545,227		$	156,365,548

See notes to financial statements.

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GATX Corporation Salaried Employees Retirement Savings Plan

Notes to Financial Statements

EIN 36-1124040
Plan #002

1. Description of the Plan

The following description of the GATX Corporation (GATX or the Company) Salaried Employees Retirement Savings Plan (the Plan) provides only general information. Participants should refer to the plan document for a more complete description of the Plan’s provisions.

General

The Plan is a defined-contribution plan, established July 1, 1965, for salaried employees of GATX and each of its domestic subsidiaries, which adopt the Plan upon authorization by GATX. The Plan is subject to the provisions of the Employee Retirement Income Security Act of 1974 (ERISA).

Contributions

Each year participants may make basic contributions of 1% to 50% of eligible pretax compensation, as defined in the Plan (as defined), and participants who have attained the age of 50 before the close of the plan year may make catch-up contributions of 1% to 25% of eligible pretax compensation. Participants may also contribute amounts representing distributions from other qualified defined-benefit or defined-contribution plans.

After a participant completes six months of service, the Company contributes on behalf of the participant a matching contribution of $0.50 for each $1.00 contributed by the participant, up to 6% of the participant’s eligible compensation. At its discretion, the Company may make an additional matching contribution for eligible participants. All contributions are made in cash and are deposited semimonthly.

Participant Accounts

Each participant’s account is credited with the participant’s contributions, the Company’s contributions, and an allocation of the Plan’s earnings (losses). Allocations are based on account balances (as defined). The benefit to which a participant is entitled is the benefit that can be provided from the participant’s account.

Vesting

Participants are immediately 100% vested in their account balance.

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GATX Corporation Salaried Employees Retirement Savings Plan

Notes to Financial Statements (continued)

1. Description of the Plan (continued)

Investment Options

Investment alternatives for participant contributions consist of the GATX Stock Fund, which is held in a Master Trust; the Fidelity Managed Income Portfolio II (the Fidelity MIP Fund), the Bank of New York Mid-Cap Index and Pyramis Small Capitalization, which are all common collective trusts; and selected mutual fund options available through Fidelity Management Trust Company.

Participants may change their investment options on any business day.

Benefit Payments

In the event of retirement (as defined), death, permanent disability, or termination of employment, the balance in the participant’s account will be distributed to the participant or the participant’s beneficiary in a single lump-sum cash payment, installments, or an annuity. The portion of the participant’s account invested in GATX stock may be distributed in kind. In-service withdrawals are available to participants for immediate and heavy financial need (as defined). The Plan also allows for age 59 1/2 withdrawals (as defined).

Administrative Expenses

It is the intent of the Company to pay the administrative expenses of the Plan, but if the Company fails to make the payments, or so directs, there may be a charge against the Plan for these expenses.

Participant Loans

A participant may borrow an amount up to the lesser of $50,000 or 50% of their account balance. Such loans, which are payable over a term specified by the Plan, bear interest at a reasonable rate and are secured by the participant’s account balance in the Plan.

Plan Termination

Although it has not expressed any intent to do so, the Company has the right under the Plan to terminate the Plan subject to the provisions of ERISA. In the event of Plan termination, participants remain 100% vested in their account balances.

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GATX Corporation Salaried Employees Retirement Savings Plan

Notes to Financial Statements (continued)

2. Significant Accounting Policies

New Accounting Pronouncements

In September 2006, the Financial Accounting Standards Board issued Statement of Financial Accounting Standards No. 157, Fair Value Measurements (“SFAS No. 157”). SFAS No. 157 defines fair value, establishes a framework for measuring fair value and requires enhanced disclosures about fair value measurements. SFAS No. 157 defines fair value as “the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.” SFAS No. 157 is effective for fiscal years beginning after November 15, 2007. The application of SFAS No. 157 is not expected to be material to the Plan’s financial statements.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires the plan administrator to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.

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GATX Corporation Salaried Employees Retirement Savings Plan

Notes to Financial Statements (continued)

2. Significant Accounting Policies (continued)

Investment Valuation and Income Recognition

Shares of mutual funds are valued at quoted market prices, which represent the net asset values of shares held by the Plan at year-end. The GATX Stock Fund (the Fund) is tracked on a unitized basis. The Fund consists of shares of GATX common stock and funds held in the Fidelity Cash Reserves Fund sufficient to meet the Fund’s daily cash needs. Unitizing the Fund allows for daily trades into and out of the Fund. The value of a unit reflects the combined market value of GATX common stock and the cash investments held by the Fund. At December 31, 2007 and 2006, the value of a unit was $21.92 and $25.29, respectively. Participant loans are valued at their outstanding balances, which approximate fair value.

The Fidelity MIP Fund contains investments in fully benefit-responsive insurance contracts that provide that the Plan may make withdrawals at contract value for benefit-responsive requirements. The Plan’s investment in units of the Fidelity MIP Fund is presented at fair value in the statements of assets available for benefits, with an adjustment to its contract value separately disclosed. The contract value is the relevant measurement attribute for that portion of the net assets available for benefits of a defined contribution plan attributable to fully benefit-responsive investment contracts because contract value is the amount participants would receive if they were to initiate permitted transactions under the terms of the Plan. The contract value of the Fidelity MIP Fund represents contributions plus earnings, less participant withdrawals and administrative expenses.

A summary of the fair value and contract value of the Fidelity MIP Fund is as follows:

	December 31
	2007		2006
Fidelity MIP Fund, at fair value	$	25,728,630	$	27,603,361
Fidelity MIP Fund, at contract value		25,535,033		27,276,315

Purchases and sales of securities are recorded on a trade-date basis. Interest income is recorded on the accrual basis. Dividends are recorded on the ex-dividend date.

Contributions

Participant contributions are made through payroll deductions and are recorded in the period the deductions are made.

9

GATX Corporation Salaried Employees Retirement Savings Plan

Notes to Financial Statements (continued)

3. Risks and Uncertainties

The Plan invests in various investment securities. Investment securities are exposed to various risks such as interest rate, market, and credit risks. Due to the level of risk associated with certain investment securities, it is at least reasonably possible that changes in the values of investment securities will occur in the near term and that such changes could materially affect participants’ account balances and the amounts reported in the statements of assets available for benefits.

4. Investments

Except for investments held in the Master Trust (see Note 5), the Plan held the following individual investments at fair value representing 5% or more of the Plan’s assets:

	December 31
	2007		2006
Fidelity Managed Income Portfolio II	$	25,535,033	$	27,276,315
Spartan U.S. Equity Index Fund		20,841,114		22,899,433
Eaton Vance Large Cap Value Fund (A)		14,729,668		—
PIMCO Total Return Fund — Institutional Class		9,161,481		9,717,770
Fidelity Diversified International Fund		8,566,373		6,803,237
T. Rowe Price Growth Stock Fund — Advisory Class		7,851,946		—
Fidelity Equity-Income Fund		—		15,436,395
Putnam Voyager Fund A		—		7,659,828
Vanguard Extended Market Index		—		7,187,136

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GATX Corporation Salaried Employees Retirement Savings Plan

Notes to Financial Statements (continued)

5. Master Trust

The GATX Stock Fund is in a Master Trust, which includes assets of the Plan and of the GATX Corporation Hourly Employees Retirement Savings Plan. The Plan’s interest in the Master Trust is stated at the Plan’s equity in the net assets of the Master Trust at December 31, 2007 and 2006.

A summary of the net assets and the changes in net assets of the Master Trust is as follows:

	December 31
	2007			2006
Assets
Cash	$	—		$	192,746
GATX common stock		29,383,927			39,096,892
Other receivables		25,645			27,204
Liabilities
Other payables		(8,829	)		(162,661	)
Net assets	$	29,400,743		$	39,154,181

	Year Ended December 31
	2007			2006
Additions
Transfers in from participating plans	$	3,243,381		$	6,584,965
Interest and dividend income		45,403			904,375
		3,288,784			7,489,340
Deductions
Transfers out to participating plans		(9,078,615	)		(13,989,267	)
Net realized and unrealized (depreciation) appreciation in fair value of common stock		(3,963,607	)		7,403,349
Net (decrease) increase in trust assets		(9,753,438	)		903,422
Net assets at beginning of year		39,154,181			38,250,759
Net assets at end of year	$	29,400,743		$	39,154,181

The Plan held a 96.5% and 96.6% interest in the Master Trust as of December 31, 2007 and 2006, respectively.

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GATX Corporation Salaried Employees Retirement Savings Plan

Notes to Financial Statements (continued)

6. Non-Participant-Directed Investments

Plan information about the net assets and the significant components of the changes in net assets relating to the GATX Stock Fund, which includes participant-directed and non-participant-directed investments, is as follows:

	December 31
	2007		2006
Investment, at fair value:
Interest in the GATX Stock Fund	$	28,379,594	$	37,823,797

	Year Ended December 31
	2007			2006
Changes in net assets:
Company contributions	$	175,564		$	496,598
Participant contributions		584,672			542,844
Rollover contributions		15,038			1,173
Interest and dividend income		62,641			874,021
Net realized and unrealized (depreciation) appreciation in fair value of common stock		(3,834,555	)		7,187,815
Benefits paid		(4,023,666	)		(4,358,860	)
Net interfund transfers		(2,443,299	)		(3,970,900	)
Other		19,402			(90,214	)
	$	(9,444,203	)	$	682,477

7. Differences Between Financial Statements and Form 5500

The following is a reconciliation of assets available for benefits per the financial statements to the Form 5500:

	Year Ended December 31
	2007			2006
Assets available for benefits at fair value, per the financial statements	$	144,351,630		$	156,038,502
Amount receivable from employer contributions		(54,296	)		(43,997	)
Assets available for benefits per Form 5500, Schedule H	$	144,297,334		$	155,994,505

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GATX Corporation Salaried Employees Retirement Savings Plan

Notes to Financial Statements (continued)

8. Income Tax Status

The Plan has received a determination letter from the Internal Revenue Service dated July 31, 2002, stating that the Plan is qualified under Section 401(a) of the Internal Revenue Code (the Code), and, therefore, the related trust is exempt from taxation. Subsequent to this determination, the Plan was amended. Once qualified, the Plan is required to operate in conformity with the Code to maintain its qualification. The plan administrator believes the Plan is being operated in compliance with the applicable requirements of the Code and, therefore, believes that the Plan, as amended, is qualified and the related trust is tax-exempt.

9. Related Party

The Plan invests in GATX common stock. GATX is the Plan’s sponsor, and, therefore, such investments are party-in-interest transactions.

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EIN 36-1124040
Plan #002

GATX Corporation Salaried Employees Retirement Savings Plan

Schedule H, Line 4i — Schedule of Assets
(Held at End of Year)

December 31, 2007

	Shares/		Current
Identity of Issuer/Description of Issue	Units		Value
Fidelity Management Trust Company*:
Fidelity Managed Income Portfolio II*		25,728,630	$	25,535,033
Spartan U.S. Equity Index Fund		401,563		20,841,114
Eaton Vance Large Cap Value Fund (A)		654,071		14,729,668
PIMCO Total Return Fund — Institutional Class		857,014		9,161,481
Fidelity Diversified International		214,696		8,566,373
T.Rowe Price Growth Stock -Advisory Class		235,088		7,851,946
Bank of New York Mid-Cap Index		591,718		6,047,356
Pyramis Small Capitalization		564,078		5,595,650
Alliance Bernstein International Value K		239,464		5,287,370
Vanguard Target Return 2020		139,172		3,266,364
Vanguard Target Return 2030		72,652		1,733,478
Vanguard Target Return 2010		73,681		1,699,082
Vanguard Target Return 2040		52,420		1,246,012
Vanguard Targeted Return Inc		84,348		938,790
Vanguard Target Return 2005		54,397		653,851
Vanguard Target Return 2015		46,494		607,205
Vanguard Target Return 2025		30,293		415,626
Vanguard Target Return 2035		6,139		89,749
Vanguard Target Return 2045		4,856		73,279
Vanguard Target Return 2050		563		13,439
Participant loans (5% to 11% interest rates, various maturities)				1,564,874
			$	115,917,740

* Party in interest to the Plan.

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SIGNATURE

Pursuant to the requirements of the Securities and Exchange Act of 1934, the trustees (or other persons who administer the employee benefit plan) have duly caused this annual report to be signed by the undersigned thereunto duly authorized.

	GATX CORPORATION SALARIED EMPLOYEES RETIREMENT SAVINGS PLAN (Name of the Plan)
Date: June 23, 2008	/s/ Malinda Riley
	Malinda Riley
	Plan Administrator

15

EXHIBIT INDEX

     The following exhibit is filed as part of this annual report:

Exhibit
	23.1	Consent of Independent Registered Public Accounting Firm

16