Filed Pursuant to Rule 424(b)(3)
                                          REGISTRATION NO. 333-15819 
  



         PROSPECTUS SUPPLEMENT NO. 1 DATED FEBRUARY 21, 1997
      TO THE PROSPECTUS DATED NOVEMBER 8, 1996 OF IMMUNOGEN, INC.



     This Prospectus Supplement No. 1 amends the information in the section
entitled "Selling Stockholders" in the Prospectus dated November 8, 1996.  
Brown Simpson, LLC has entered into an agreement with Dr. Michael E. Lewis 
("Dr. Lewis") whereby 5,000 of the 62,500 warrants to purchase ImmunoGen 
Common Stock, $.01 par value per share, ("Common Stock") owned by Brown 
Simpson, LLC ("Brown Simpson") have been transferred to Dr. Lewis.  In
order to reflect Dr. Lewis as a potential Selling Stockholder hereunder, 
and assuming for such purposes that the warrants to purchase all 62,500 
shares are exercised, the Selling Stockholder table is amended by deleting 
the information as to Brown Simpson as Selling Stockholder with respect to 
62,500 shares of Common Stock and substituting therefor the following 
information:

                    Shares Owned Prior                     Shares Owned After
                       to Offering                            Offering(1)
                       -----------      Number of Shares      -----------
Selling Stockholder Number    Percent     Being Offered     Number     Percent
- ------------------- --------  -------   ----------------   --------    -------
Brown Simpson       57,500(2)   *          57,500            0           --     
  
Dr. Lewis            5,000(3)   *           5,000            0           --
  
*Less than 1%.

(1)  Assumes the sale of all shares offered hereby to unaffiliated third 
parties.

(2)  Based on 18,390,984 shares of Common Stock outstanding on February 20, 
1997 and adjusted to reflect the transfer by Brown Simpson of 5,000 warrants 
to purchase Common Stock to Dr. Lewis.

(3) Assumes the transfer of warrants to Dr. Lewis and adjusted to reflect the
exercise of the warrants by Dr. Lewis into 5,000 shares of Common Stock.


This Prospectus Supplement No. 1 should be read in conjunction
with the Prospectus dated November 8, 1996.

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