1
                                                                    Exhibit 99.1



IMMUNOGEN CONTACT:           Mitchel Sayare, Ph.D.
                             Chairman and CEO
                             ImmunoGen, Inc.
                             (781)769-4242
                             www.immunogen.com


FOR IMMEDIATE RELEASE


               ImmunoGen, Inc. Appoints Mark Skaletsky of GelTex
                  Pharmaceuticals, Inc. to Board of Directors

CAMBRIDGE,  Mass., May 16 -- ImmunoGen,  Inc.  (Nasdaq:  IMGN - news) named Mark
Skaletsky  to its Board of  Directors.  Mr.  Skaletsky  is CEO and  President of
GelTex  Pharmaceuticals,  Inc. GelTex develops and markets non- absorbed polymer
drugs that selectively bind and eliminate target  substances from the intestinal
tract.

"We are  genuinely  pleased to have Mark join our Board at this pivotal time in
ImmunoGen's  development,"  stated Mitchel Sayare,  Ph.D.,  Chairman and CEO of
ImmunoGen,  Inc. "The extensive experience and perspective Mark brings with him
will be a real asset as we establish  arrangements  with other companies for the
use of our technology with their monoclonal antibodies."

Mr.  Skaletsky  said,  "This is an exciting time to  participate in ImmunoGen's
development. With its novel Tumor-Activated Prodrug approach to cancer treatment
and the potential  development  of  additional  Tumor-Activated  Prodrugs  using
ImmunoGen's technology and antibodies from other sources, ImmunoGen is poised to
become a substantially  different  company. I look forward to the opportunity of
adding the value of my experience to the future of ImmunoGen."

Mr.  Skaletsky has been  President and CEO of GelTex  Pharmaceuticals,  Inc., of
Waltham,  MA since 1993.  Prior to that he was  President,  CEO and  Chairman of
Enzytech,  Inc.,  and  President  and COO of Biogen,  Inc.  Mr.  Skaltesky  is a
chairman of the board of directors of the Biotechnology  Industry  Organization,
and is a director of Isis Pharmaceuticals and Microcide. He is also a Trustee of
Bentley College.

ImmunoGen,  Inc. develops  innovative  biopharmaceuticals,  primarily for cancer
treatment. The Company has created potent Tumor-Activated  Prodrugs,  consisting
of low-molecular weight chemicals coupled to monoclonal antibodies, for delivery
to and destruction of cancer cells.

This press release  includes  forward-looking  statements  based on management's
current  expectations.  Factors  that  could  cause  future  results  to  differ
materially from such expectations  include,  but are not limited to: the ability
to secure future funding;  the success of the Company's research  strategy;  the
applicability of the discoveries made therein; the difficulties  inherent in the
development of  pharmaceuticals,  including  uncertainties  as to the timing and
results  of  preclinical  studies;  uncertainty  as  to  whether  the  Company's
potential  products will succeed in human clinical  trials and uncertainty as to
the results of such trials; uncertainty as to whether adequate reimbursement for
these  products  will exist from  government,  private  healthcare  insurers and
third-party  payors; and the uncertainties as to the extent of future government
regulation of the pharmaceutical business.

                                       ###