Directors
Mitchel Sayare, Ph.D.
Chairman, President, and
Chief Executive Officer,
ImmunoGen, Inc.

Walter A. Blättler, Ph.D.
Executive Vice President,
Science and Technology,
ImmunoGen, Inc.

David W. Carter
Chairman and Chief Executive Officer,
Xenogen Corporation

Stuart F. Feiner
Executive Vice President,
General Counsel, and Secretary,
Inco Limited

Nicole Onetto, M.D.
Senior Vice President,
Product Development and
Chief Medical Officer,
ZymoGenetics, Inc.

Mark Skaletsky
Chairman and Chief Executive Officer,
Trine Pharmaceuticals, Inc.

Joseph J. Villafranca, Ph.D.
Executive Vice President,
Pharmaceutical Drug Development
and Operations,
Neose Technologies, Inc.

Executive Officers
Mitchel Sayare, Ph.D.
President and Chief Executive Officer

Walter A. Blättler, Ph.D.
Executive Vice President,
Science and Technology

Daniel M. Junius
Senior Vice President, Finance and
Chief Financial Officer

John M. Lambert, Ph.D.
Senior Vice President,
Pharmaceutical Development

Pauline Jen Ryan
Senior Vice President,
Corporate Development and Operations

Corporate Headquarters
ImmunoGen, Inc.
128 Sidney Street
Cambridge, Massachusetts 02139
617 995 2500
www.immunogen.com

Annual Meeting
10:00 AM on November 8, 2005
At the Offices of the Company
128 Sidney Street
Cambridge, Massachusetts 02139

Transfer Agent and Registrar
Mellon Investor Services LLC
Overpeck Center
85 Challenger Road
Ridgefield Park, New Jersey 07660-2108
800 288 9541
www.melloninvestor.com/isd

Legal Counsel
Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
Boston, Massachusetts

Auditors
Ernst & Young LLP
Boston, Massachusetts

Shareholder Inquiries
Information about ImmunoGen can be found at www.immunogen.com. Inquiries related to the Company may be directed to the Investor Relations department at our headquarters. Communications related to stock and transfer requirements, including lost stock certificates and change of name or address, should be directed to the Transfer Agent.