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

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

John M. Lambert, Ph.D.

Senior Vice President,
Pharmaceutical Development

Virginia Lavery

Vice President, Finance and Treasurer

Pauline Jen Ryan

Senior Vice President,
Business Development

Corporate Headquarters

ImmunoGen, Inc.

128 Sidney Street

Cambridge, Massachusetts 02139

(617) 995-2500

www.immunogen.com

Annual Meeting

Tuesday, November 9, 2004

At the Offices of the Company

128 Sidney Street

Cambridge, Massachusetts 02139

Transfer Agent and Registrar

Mellon Investor Services LLC

85 Challenger Road

Ridgefield Park, New Jersey 07660

(201) 329-8660

(800) 288-9541

www.melloninvestor.com

Legal Counsel

Mintz, Levin, Cohn, Ferris,
Glovsky and Popeo, P.C.

Boston, Massachusetts

Auditors

Ernst & Young LLP

Boston, Massachusetts