<PAGE>
              As filed with the Securities and Exchange Commission
                              On December 18, 2001

                              Registration No. 33-


                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT

                                      UNDER

                           THE SECURITIES ACT OF 1933

                                 IMMUNOGEN, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)


                MASSACHUSETTS                            04-2726691
       (STATE OR OTHER JURISDICTION OF                (I.R.S. EMPLOYER
        INCORPORATION OR ORGANIZATION)               IDENTIFICATION NO.)


                128 SIDNEY STREET, CAMBRIDGE, MASSACHUSETTS 02139
                    (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)


                   IMMUNOGEN, INC. RESTATED STOCK OPTION PLAN
                            (FULL TITLE OF THE PLAN)


                                 Mitchel Sayare
                            Chairman of the Board and
                             Chief Executive Officer
                                 ImmunoGen, Inc.
                                128 Sidney Street
                         CAMBRIDGE, MASSACHUSETTS 02139
                     (NAME AND ADDRESS OF AGENT FOR SERVICE)

                                 (617) 995-2500
          (TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                  Please send copies of all communications to:

                            Jonathan L. Kravetz, Esq.
                           Mintz, Levin, Cohn, Ferris,
                             Glovsky and Popeo, P.C.
                              One Financial Center
                                Boston, MA 02111
                                 (617) 542-6000


                                       1
<PAGE>


                                                                      1
                         CALCULATION OF REGISTRATION FEE

<TABLE>
<S>                 <C>               <C>           <C>           <C>
                                       Proposed       Proposed
Title of                               maximum        maximum
securities           Amount            offering       aggregate    Amount of
to be                to be             price per      offering     registration
registered           registered(1)     unit(2)        price(2)     fee

Common Stock,
$.01 par value        2,500,000         $16.10       $40,250,000    $9,619.75
                      =========         ======       ===========    =========
</TABLE>



(1)  The number of shares of common stock, par value $.01 per share (the "Common
     Stock"), consists of the aggregate number of additional shares not
     previously registered which may be sold upon the exercise of options which
     may hereafter be granted under the ImmunoGen, Inc. Restated Stock Option
     Plan (the "Plan"). The maximum number of shares which may be sold upon the
     exercise of such options granted under the Plan is subject to adjustment in
     accordance with certain anti-dilution and other provisions of the Plan.
     Accordingly, pursuant to Rule 416 under the Securities Act of 1933, as
     amended (the "Securities Act"), this Registration Statement covers, in
     addition to the number of shares stated above, an indeterminable number of
     shares which may be subject to grant or otherwise issuable after the
     operation of any such anti-dilution and other provisions.

(2)  This calculation is made solely for the purpose of determining the
     registration fee pursuant to the provisions of Rules 457(c) and 457(h)
     under the Securities Act of 1933, as amended and based upon the average of
     the high and low sales prices per share of the Common Stock as reported on
     the Nasdaq National Market System on December 14, 2001.



EXPLANATORY NOTE

     This Registration Statement relates to the registration of 2,500,000
additional shares of Common Stock authorized for issuance under the Plan. In
accordance with the instructional Note to Part I of Form S-8 as promulgated by
the Securities and Exchange Commission, the information specified by Part I of
Form S-8 has been omitted from this Registration Statement on Form S-8 for
offers of Common Stock pursuant to the Plan. The prospectus filed as a part of
the Company's registration statement No. 333-53292 may no longer be used for
reofferings and resales of Common stock because the information in such
prospectus is no longer accurate.






                                     PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

     The following documents filed by the Registrant with the Securities and
Exchange Commission (the "Commission") are incorporated herein by reference:

     (a)  The Registrant's annual report on Form 10-K (Commission File No.
          0-17999) for the fiscal year ended June 30, 2001.

     (b)  The Registrant's quarterly report on Form 10-Q (Commission File No.
          0-17999) for the quarter ended September 30, 2001.

     (c)  The Registrant's current reports on Form 8-K filed with the Commission
          on September 7, 2001 and November 29, 2001 and on Form 8-K/A filed
          with the Commission on October 5, 2001.


                                       2
<PAGE>


     (d)  The description of the Common Stock included in the Registrant's
          Registration Statement on Form 8-A under the Securities Exchange Act
          of 1934 (File No. 0-17999), filed with the Commission on September 22,
          1989, including any amendment or report filed for the purpose of
          updating such description.

     (e)  The Registrant's proxy materials on Schedule 14A filed with the
          Commission on October 4, 2001.

     All reports and other documents subsequently filed by the Registrant with
the Commission pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange
Act prior to the filing of a post-effective amendment which indicates that all
securities covered by this Registration Statement have been sold or which
deregisters all such securities then remaining unsold shall be deemed to be
incorporated by reference herein and to be a part hereof from the date of the
filing of such reports and documents.

ITEM 4. DESCRIPTION OF SECURITIES.

     Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Incorporated herein by reference from the Registrant's Registration
Statement on Form S-3 (Registration No. 333-57234), as amended.


ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

     Not applicable.

ITEM 8. EXHIBITS.

EXHIBIT NO.       DESCRIPTION

(4.1)             Form of Common Stock Certificate (previously filed as Exhibit
                  4.2 to the Registrant's Registration Statement on Form S-1,
                  Registration No. 33-31219, as amended, and incorporated herein
                  by reference)

(4.2)             Restated Articles of Organization of the Registrant
                  (previously filed as Exhibit 3.1 to the Registrant's
                  Registration Statement on Form S-1, Registration No. 33-38883,
                  as amended, and incorporated herein by reference)

(4.3)             Amendment to Articles of Organization of Registrant

(4.4)             By-Laws, as amended, of the Registrant (previously filed as
                  Exhibit 3.2 to the Registrant's annual report on Form 10-K for
                  the fiscal year ended June 30, 1990, and incorporated herein
                  by reference)

(5.1)             Opinion of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo,
                  P.C., with respect to the legality of the shares being
                  registered

(23.1)            Consent of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  (included in opinion of counsel filed as Exhibit 5.1)

(23.2)            Consent of PricewaterhouseCoopers LLP

(24)              Power of Attorney to file future amendments (included on the
                  signature page of this Registration Statement)

(99)              ImmunoGen, Inc. Restated Stock Option Plan, as amended.


                                       3
<PAGE>


ITEM 9. UNDERTAKINGS.

     (a)  The undersigned Registrant hereby undertakes:

          (1) to file, during any period in which offers or sales are being
     made, a post-effective amendment to this Registration Statement: (i) to
     include any prospectus required by Section 10(a)(3) of the Securities Act
     of 1933; (ii) to reflect in the prospectus any facts or events arising
     after the effective date of the Registration Statement (or the most recent
     post-effective amendment thereof) which, individually or in the aggregate,
     represent a fundamental change in the information set forth in the
     Registration Statement; (iii) to include any material information with
     respect to the plan of distribution not previously disclosed in the
     Registration Statement or any material change to such information in the
     Registration Statement; notwithstanding the foregoing, any increase or
     decrease in volume of securities offered (if the total dollar value of
     securities offered would not exceed that which was registered) and any
     deviation from the low or high end of the estimated maximum offering range
     may be reflected in the form of prospectus filed with the Commission
     pursuant to Rule 424(b) of Regulation C under the Securities Act of 1933,
     as amended, if, in the aggregate, the changes in volume and price represent
     no more than a 20% change in the maximum aggregate offering price set forth
     in the "Calculation of Registration Fee" table in the effective
     Registration Statement; provided, however, that paragraphs (a)(1)(i) and
     (ii) shall not apply if the information required to be included in a
     post-effective amendment by those paragraphs is contained in periodic
     reports filed by the registrant pursuant to Section 13 or Section 15(d) of
     the Securities Exchange Act of 1934 that are incorporated by reference in
     the registration statement.

          (2) that, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment shall be deemed
     to be a new registration statement relating to the securities offered
     therein, and the offering of such securities at that time shall be deemed
     to be the initial bona fide offering thereof.

          (3) to remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

     (b)  The undersigned Registrant hereby undertakes that, for purposes of
          determining any liability under the Securities Act of 1933, each
          filing of the Registrant's annual report pursuant to Section 13(a) or
          Section 15(d) of the Securities Exchange Act of 1934 that is
          incorporated by reference in this Registration Statement shall be
          deemed to be a new registration statement relating to the securities
          offered therein, and the offering of such securities at that time
          shall be deemed to be the initial bona fide offering thereof.

     (c)  Insofar as indemnification for liabilities arising under the
          Securities Act of 1933 may be permitted to directors, officers and
          controlling persons of the Registrant pursuant to the foregoing
          provisions, or otherwise, the Registrant has been advised that in the
          opinion of the Securities and Exchange Commission such indemnification
          is against public policy as expressed in the Securities Act of 1933
          and is, therefore, unenforceable. In the event that a claim for
          indemnification against such liabilities (other than the payment by
          the Registrant of expenses incurred or paid by a director, officer or
          controlling person of the Registrant in the successful defense of any
          action, suit or proceeding) is asserted by such director, officer or
          controlling person in connection with the securities being registered,
          the Registrant will, unless in the opinion of its counsel the matter
          has been settled by controlling precedent, submit to a court of
          appropriate jurisdiction the question whether such indemnification by
          it is against public policy as expressed in the Securities Act of 1933
          and will be governed by the final adjudication of such issue.




                                       4
<PAGE>


                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Cambridge, Commonwealth of Massachusetts, on December
17, 2001.

                                       IMMUNOGEN, INC.


                                       /s/ Mitchel Sayare
                                       --------------------------------
                                       By:  Mitchel Sayare
                                            Chairman of the Board
                                            and Chief Executive Officer

     We, the undersigned officers and directors of ImmunoGen, Inc., hereby
severally constitute and appoint Mitchel Sayare and Walter Blattler and each of
them singly, as true and lawful attorneys, with full power to them and each of
them singly, to sign for us in our names in the capacities indicated below, all
additional amendments to this registration statement, and generally to do all
things in our names and on our behalf in such capacities to enable ImmunoGen,
Inc. to comply with the provisions of the Securities Act of 1933, as amended,
and all applicable requirements of the Securities and Exchange Commission.

     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

<TABLE>
<CAPTION>
                                  Title:                                Date:
<S>                       <C>                                   <C>
/s/ Mitchel Sayare         Chairman of the Board                 December 17, 2001
----------------------     of Directors and
  Mitchel Sayare           Chief Executive Officer
                           (principal executive officer)


/s/ Gregg D. Beloff        Vice President and Chief              December 17, 2001
----------------------     Financial Officer
  Gregg D. Beloff          (principal accounting officer)

/s/ Walter A. Blattler
----------------------     Executive Vice President,             December 17, 2001
  Walter A. Blattler       Science and Technology,
                           and Director


/s/ David W. Carter        Director                              December 17, 2001
----------------------
  David W. Carter


/s/ Michael R. Eisenson    Director                              December 17, 2001
---------------------
  Michael R. Eisenson


/s/ Stuart F. Feiner       Director                              December 17, 2001
---------------------
  Stuart F. Feiner


/s/ Mark B. Skaletsky      Director                              December 17, 2001
---------------------
  Mark B. Skaletsky

</TABLE>


                                       5
<PAGE>



                                 IMMUNOGEN, INC.

                                  EXHIBIT INDEX



EXHIBIT NO.       DESCRIPTION

(4.1)             Form of Common Stock Certificate (previously filed as Exhibit
                  4.2 to the Registrant's Registration Statement on Form S-1,
                  Registration No. 33-31219, as amended, and incorporated herein
                  by reference)

(4.2)             Restated Articles of Organization of the Registrant
                  (previously filed as Exhibit 3.1 to the Registrant's
                  Registration Statement on Form S-1, Registration No. 33-38883,
                  as amended, and incorporated herein by reference)

(4.3)             Amendment to Articles of Organization of Registrant

(4.4)             By-Laws, as amended, of the Registrant (previously filed as
                  Exhibit 3.2 to the Registrant's annual report on Form 10-K for
                  the fiscal year ended June 30, 1990, and incorporated herein
                  by reference)

(5.1)             Opinion of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo,
                  P.C., with respect to the legality of the shares being
                  registered

(23.1)            Consent of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  (included in opinion of counsel filed as Exhibit 5.1)

(23.2)            Consent of PricewaterhouseCoopers LLP

(24)              Power of Attorney to file future amendments (included on the
                  signature page of this Registration Statement)

(99)              ImmunoGen, Inc. Restated Stock Option Plan (as amended)




                                       6
[{"type": "S-8", "sequence": "1", "filename": "a2066249zs-8.txt", "description": "FORM S-8", "secsgml_size_bytes": 17681}]
{"company-data": {"conformed-name": "IMMUNOGEN INC", "cik": "0000855654", "assigned-sic": "2834", "irs-number": "042726691", "state-of-incorporation": "MA", "fiscal-year-end": "0630"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-75372", "film-number": "1816815"}, "business-address": {"street1": "128 SIDNEY ST", "city": "CAMBRIDGE", "state": "MA", "zip": "02139", "phone": "6176619312"}, "mail-address": {"street1": "128 SIDENEY ST", "city": "CAMBRIDGE", "state": "MA", "zip": "02139"}}
As filed with the Securities and Exchange Commission
                              On December 18, 2001

                              Registration No. 33-

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT

                                      UNDER

                           THE SECURITIES ACT OF 1933

                                 IMMUNOGEN, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

                MASSACHUSETTS                            04-2726691
       (STATE OR OTHER JURISDICTION OF                (I.R.S. EMPLOYER
        INCORPORATION OR ORGANIZATION)               IDENTIFICATION NO.)

                128 SIDNEY STREET, CAMBRIDGE, MASSACHUSETTS 02139
                    (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)

                   IMMUNOGEN, INC. RESTATED STOCK OPTION PLAN
                            (FULL TITLE OF THE PLAN)

                                 Mitchel Sayare
                            Chairman of the Board and
                             Chief Executive Officer
                                 ImmunoGen, Inc.
                                128 Sidney Street
                         CAMBRIDGE, MASSACHUSETTS 02139
                     (NAME AND ADDRESS OF AGENT FOR SERVICE)

                                 (617) 995-2500
          (TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                  Please send copies of all communications to:

                            Jonathan L. Kravetz, Esq.
                           Mintz, Levin, Cohn, Ferris,
                             Glovsky and Popeo, P.C.
                              One Financial Center
                                Boston, MA 02111
                                 (617) 542-6000

                                       1
1
                         CALCULATION OF REGISTRATION FEE
Proposed       Proposed
Title of                               maximum        maximum
securities           Amount            offering       aggregate    Amount of
to be                to be             price per      offering     registration
registered           registered(1)     unit(2)        price(2)     fee

Common Stock,
$.01 par value        2,500,000         $16.10       $40,250,000    $9,619.75
                      =========         ======       ===========    =========
(1)  The number of shares of common stock, par value $.01 per share (the "Common
     Stock"), consists of the aggregate number of additional shares not
     previously registered which may be sold upon the exercise of options which
     may hereafter be granted under the ImmunoGen, Inc. Restated Stock Option
     Plan (the "Plan"). The maximum number of shares which may be sold upon the
     exercise of such options granted under the Plan is subject to adjustment in
     accordance with certain anti-dilution and other provisions of the Plan.
     Accordingly, pursuant to Rule 416 under the Securities Act of 1933, as
     amended (the "Securities Act"), this Registration Statement covers, in
     addition to the number of shares stated above, an indeterminable number of
     shares which may be subject to grant or otherwise issuable after the
     operation of any such anti-dilution and other provisions.

(2)  This calculation is made solely for the purpose of determining the
     registration fee pursuant to the provisions of Rules 457(c) and 457(h)
     under the Securities Act of 1933, as amended and based upon the average of
     the high and low sales prices per share of the Common Stock as reported on
     the Nasdaq National Market System on December 14, 2001.

EXPLANATORY NOTE

     This Registration Statement relates to the registration of 2,500,000
additional shares of Common Stock authorized for issuance under the Plan. In
accordance with the instructional Note to Part I of Form S-8 as promulgated by
the Securities and Exchange Commission, the information specified by Part I of
Form S-8 has been omitted from this Registration Statement on Form S-8 for
offers of Common Stock pursuant to the Plan. The prospectus filed as a part of
the Company's registration statement No. 333-53292 may no longer be used for
reofferings and resales of Common stock because the information in such
prospectus is no longer accurate.

                                     PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

     The following documents filed by the Registrant with the Securities and
Exchange Commission (the "Commission") are incorporated herein by reference:

     (a)  The Registrant's annual report on Form 10-K (Commission File No.
          0-17999) for the fiscal year ended June 30, 2001.

     (b)  The Registrant's quarterly report on Form 10-Q (Commission File No.
          0-17999) for the quarter ended September 30, 2001.

     (c)  The Registrant's current reports on Form 8-K filed with the Commission
          on September 7, 2001 and November 29, 2001 and on Form 8-K/A filed
          with the Commission on October 5, 2001.

                                       2
(d)  The description of the Common Stock included in the Registrant's
          Registration Statement on Form 8-A under the Securities Exchange Act
          of 1934 (File No. 0-17999), filed with the Commission on September 22,
          1989, including any amendment or report filed for the purpose of
          updating such description.

     (e)  The Registrant's proxy materials on Schedule 14A filed with the
          Commission on October 4, 2001.

     All reports and other documents subsequently filed by the Registrant with
the Commission pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange
Act prior to the filing of a post-effective amendment which indicates that all
securities covered by this Registration Statement have been sold or which
deregisters all such securities then remaining unsold shall be deemed to be
incorporated by reference herein and to be a part hereof from the date of the
filing of such reports and documents.

ITEM 4. DESCRIPTION OF SECURITIES.

     Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Incorporated herein by reference from the Registrant's Registration
Statement on Form S-3 (Registration No. 333-57234), as amended.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

     Not applicable.

ITEM 8. EXHIBITS.

EXHIBIT NO.       DESCRIPTION

(4.1)             Form of Common Stock Certificate (previously filed as Exhibit
                  4.2 to the Registrant's Registration Statement on Form S-1,
                  Registration No. 33-31219, as amended, and incorporated herein
                  by reference)

(4.2)             Restated Articles of Organization of the Registrant
                  (previously filed as Exhibit 3.1 to the Registrant's
                  Registration Statement on Form S-1, Registration No. 33-38883,
                  as amended, and incorporated herein by reference)

(4.3)             Amendment to Articles of Organization of Registrant

(4.4)             By-Laws, as amended, of the Registrant (previously filed as
                  Exhibit 3.2 to the Registrant's annual report on Form 10-K for
                  the fiscal year ended June 30, 1990, and incorporated herein
                  by reference)

(5.1)             Opinion of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo,
                  P.C., with respect to the legality of the shares being
                  registered

(23.1)            Consent of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  (included in opinion of counsel filed as Exhibit 5.1)

(23.2)            Consent of PricewaterhouseCoopers LLP

(24)              Power of Attorney to file future amendments (included on the
                  signature page of this Registration Statement)

(99)              ImmunoGen, Inc. Restated Stock Option Plan, as amended.

                                       3
ITEM 9. UNDERTAKINGS.

     (a)  The undersigned Registrant hereby undertakes:

          (1) to file, during any period in which offers or sales are being
     made, a post-effective amendment to this Registration Statement: (i) to
     include any prospectus required by Section 10(a)(3) of the Securities Act
     of 1933; (ii) to reflect in the prospectus any facts or events arising
     after the effective date of the Registration Statement (or the most recent
     post-effective amendment thereof) which, individually or in the aggregate,
     represent a fundamental change in the information set forth in the
     Registration Statement; (iii) to include any material information with
     respect to the plan of distribution not previously disclosed in the
     Registration Statement or any material change to such information in the
     Registration Statement; notwithstanding the foregoing, any increase or
     decrease in volume of securities offered (if the total dollar value of
     securities offered would not exceed that which was registered) and any
     deviation from the low or high end of the estimated maximum offering range
     may be reflected in the form of prospectus filed with the Commission
     pursuant to Rule 424(b) of Regulation C under the Securities Act of 1933,
     as amended, if, in the aggregate, the changes in volume and price represent
     no more than a 20% change in the maximum aggregate offering price set forth
     in the "Calculation of Registration Fee" table in the effective
     Registration Statement; provided, however, that paragraphs (a)(1)(i) and
     (ii) shall not apply if the information required to be included in a
     post-effective amendment by those paragraphs is contained in periodic
     reports filed by the registrant pursuant to Section 13 or Section 15(d) of
     the Securities Exchange Act of 1934 that are incorporated by reference in
     the registration statement.

          (2) that, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment shall be deemed
     to be a new registration statement relating to the securities offered
     therein, and the offering of such securities at that time shall be deemed
     to be the initial bona fide offering thereof.

          (3) to remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

     (b)  The undersigned Registrant hereby undertakes that, for purposes of
          determining any liability under the Securities Act of 1933, each
          filing of the Registrant's annual report pursuant to Section 13(a) or
          Section 15(d) of the Securities Exchange Act of 1934 that is
          incorporated by reference in this Registration Statement shall be
          deemed to be a new registration statement relating to the securities
          offered therein, and the offering of such securities at that time
          shall be deemed to be the initial bona fide offering thereof.

     (c)  Insofar as indemnification for liabilities arising under the
          Securities Act of 1933 may be permitted to directors, officers and
          controlling persons of the Registrant pursuant to the foregoing
          provisions, or otherwise, the Registrant has been advised that in the
          opinion of the Securities and Exchange Commission such indemnification
          is against public policy as expressed in the Securities Act of 1933
          and is, therefore, unenforceable. In the event that a claim for
          indemnification against such liabilities (other than the payment by
          the Registrant of expenses incurred or paid by a director, officer or
          controlling person of the Registrant in the successful defense of any
          action, suit or proceeding) is asserted by such director, officer or
          controlling person in connection with the securities being registered,
          the Registrant will, unless in the opinion of its counsel the matter
          has been settled by controlling precedent, submit to a court of
          appropriate jurisdiction the question whether such indemnification by
          it is against public policy as expressed in the Securities Act of 1933
          and will be governed by the final adjudication of such issue.

                                       4
SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Cambridge, Commonwealth of Massachusetts, on December
17, 2001.

                                       IMMUNOGEN, INC.

                                       /s/ Mitchel Sayare
                                       --------------------------------
                                       By:  Mitchel Sayare
                                            Chairman of the Board
                                            and Chief Executive Officer

     We, the undersigned officers and directors of ImmunoGen, Inc., hereby
severally constitute and appoint Mitchel Sayare and Walter Blattler and each of
them singly, as true and lawful attorneys, with full power to them and each of
them singly, to sign for us in our names in the capacities indicated below, all
additional amendments to this registration statement, and generally to do all
things in our names and on our behalf in such capacities to enable ImmunoGen,
Inc. to comply with the provisions of the Securities Act of 1933, as amended,
and all applicable requirements of the Securities and Exchange Commission.

     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.
Title:                                Date:
/s/ Mitchel Sayare         Chairman of the Board                 December 17, 2001
----------------------     of Directors and
  Mitchel Sayare           Chief Executive Officer
                           (principal executive officer)

/s/ Gregg D. Beloff        Vice President and Chief              December 17, 2001
----------------------     Financial Officer
  Gregg D. Beloff          (principal accounting officer)

/s/ Walter A. Blattler
----------------------     Executive Vice President,             December 17, 2001
  Walter A. Blattler       Science and Technology,
                           and Director

/s/ David W. Carter        Director                              December 17, 2001
----------------------
  David W. Carter

/s/ Michael R. Eisenson    Director                              December 17, 2001
---------------------
  Michael R. Eisenson

/s/ Stuart F. Feiner       Director                              December 17, 2001
---------------------
  Stuart F. Feiner

/s/ Mark B. Skaletsky      Director                              December 17, 2001
---------------------
  Mark B. Skaletsky
5
IMMUNOGEN, INC.

                                  EXHIBIT INDEX

EXHIBIT NO.       DESCRIPTION

(4.1)             Form of Common Stock Certificate (previously filed as Exhibit
                  4.2 to the Registrant's Registration Statement on Form S-1,
                  Registration No. 33-31219, as amended, and incorporated herein
                  by reference)

(4.2)             Restated Articles of Organization of the Registrant
                  (previously filed as Exhibit 3.1 to the Registrant's
                  Registration Statement on Form S-1, Registration No. 33-38883,
                  as amended, and incorporated herein by reference)

(4.3)             Amendment to Articles of Organization of Registrant

(4.4)             By-Laws, as amended, of the Registrant (previously filed as
                  Exhibit 3.2 to the Registrant's annual report on Form 10-K for
                  the fiscal year ended June 30, 1990, and incorporated herein
                  by reference)

(5.1)             Opinion of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo,
                  P.C., with respect to the legality of the shares being
                  registered

(23.1)            Consent of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  (included in opinion of counsel filed as Exhibit 5.1)

(23.2)            Consent of PricewaterhouseCoopers LLP

(24)              Power of Attorney to file future amendments (included on the
                  signature page of this Registration Statement)

(99)              ImmunoGen, Inc. Restated Stock Option Plan (as amended)

                                       6