Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statement on Form S-8 pertaining to the 2004 Equity Incentive Compensation Plan, the 1995 Long-Term Incentive Compensation Plan, and the 1985 Long-Term Incentive Compensation Plan of GATX Corporation of our report dated January 29, 2004, with respect to the consolidated financial statements and schedules of GATX Corporation included in its Annual Report (Form 10-K) for the year ended December 31, 2003, filed with the Securities and Exchange Commission.

ERNST & YOUNG LLP

Chicago, Illinois
June 18, 2004