<PAGE>

              As filed with the Securities and Exchange Commission
                              on December 21, 1999

                                                      Registration No. 333-_____

-------------------------------------------------------------------------------
-------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D. C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                        MILLENNIUM PHARMACEUTICALS, INC.
             (Exact name of registrant as specified in its charter)

            DELAWARE                                         04-3177038
(State or other jurisdiction of                          (I.R.S. Employer
 incorporation or organization)                        Identification Number)

     75 SIDNEY STREET, CAMBRIDGE, MASSACHUSETTS                02139
      (Address of Principal Executive Offices)              (Zip Code)

          MILLENNIUM BIOTHERAPEUTICS, INC. 1997 EQUITY INCENTIVE PLAN
                            (Full title of the Plan)

                                  MARK J. LEVIN
                             CHIEF EXECUTIVE OFFICER
                        MILLENNIUM PHARMACEUTICALS, INC.
                                75 SIDNEY STREET
                         CAMBRIDGE, MASSACHUSETTS 02139

                                 WITH A COPY TO:

       David E. Redlick, Esq.                   John B. Douglas III, Esq.
       Kenneth A. Hoxsie, Esq.                        General Counsel
         Hale and Dorr LLP                   Millennium Pharmaceuticals, Inc.
         60 State Street                            75 Sidney Street
   Boston, Massachusetts 02109               Cambridge, Massachusetts 02139
         (617) 526-6000                             (617) 679-7000

            (Name, address, including zip code, and telephone number,
                   including area code, of agents for service)

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>

                                                 Proposed                Proposed
Title of                                         Maximum                 Maximum                  Amount of
Securities               Amount to be            Offering Price          Aggregate                Registration
to be Registered         Registered              Per Share               Offering Price           Fee
----------------         ------------            --------------          --------------           ------------
<S>                     <C>                   <C>                      <C>                     <C>
Common Stock,
$.001 par value          321,000 shares          101.00 (1)              32,421,000 (1)           $ 8,560

</TABLE>

(1)  Estimated solely for the purpose of calculating the registration fee, and
     based upon the average of the high and low prices of the Common Stock on
     the Nasdaq National Market on December 17, 1999 in accordance with Rules
     457(c) and 457(h) of the Securities Act of 1933.

-------------------------------------------------------------------------------
-------------------------------------------------------------------------------

<PAGE>

                                EXPLANATORY NOTE

         This Registration Statement on Form S-8 is being filed to register the
shares of Common Stock of Millennium Pharmaceuticals, Inc. (the "Company" or
"Registrant") issuable pursuant to the Millennium BioTherapeutics, Inc. 1997
Equity Incentive Plan (the "Plan"). On December 21, 1999, pursuant to the terms
of Section 1.9 of the Agreement and Plan of Merger dated as of October 14, 1999
by and between the Company and Millennium BioTherapeutics, Inc. ("Millennium
BioTherapeutics"), the Company assumed the Plan and all of the outstanding
options to purchase Common Stock of Millennium BioTherapeutics issued under the
Plan.







                                        2

<PAGE>

PART I.       INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

              The information required by Part I is included in documents sent
or given to participants in the Plan pursuant to Rule 428(b)(1) of the
Securities Act of 1933, as amended (the "Securities Act").

PART II.      INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

         Item 3.    INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

              The following documents, which are filed with the Securities and
Exchange Commission (the "Commission"), are incorporated in this Registration
Statement by reference:

              (1) The Registrant's latest annual report filed pursuant to
         Sections 13(a) or 15(d) of the Securities Exchange Act of 1934, as
         amended (the "Exchange Act"), or the latest prospectus filed pursuant
         to Rule 424(b) under the Securities Act that contains audited financial
         statements for the Registrant's latest fiscal year for which such
         statements have been filed.

              (2) All other reports filed pursuant to Sections 13(a) or 15(d) of
         the Exchange Act since the end of the fiscal year covered by the annual
         report or the prospectus referred to in (1) above.

              (3) The description of the common stock of the Registrant, $.001
         par value per share (the "Common Stock"), contained in the Registrant's
         Registration Statement on Form 8-A filed under the Exchange Act,
         including any amendment or report filed for the purpose of updating
         such description.

              All documents subsequently filed by the Registrant 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 shares of Common Stock
offered hereby have been sold or which deregisters all shares of Common Stock
then remaining unsold, shall be deemed to be incorporated by reference herein
and to be part hereof from the date of the filing of such documents. Any
statement contained in a document incorporated or deemed to be incorporated by
reference herein shall be deemed to be modified or superseded for purposes of
this Registration Statement to the extent that a statement contained herein or
in any other subsequently filed document which also is or is deemed to be
incorporated by reference herein modifies or supersedes such statement. Any
statement so modified or superseded shall be deemed, except as so modified or
superseded, to constitute a part of this Registration Statement.

         Item 4.    DESCRIPTION OF SECURITIES

              Not applicable.

         Item 5.    INTERESTS OF NAMED EXPERTS AND COUNSEL

              Not Applicable.

         Item 6.    INDEMNIFICATION OF DIRECTORS AND OFFICERS

              Section 102 of the Delaware General Corporation Law allows a
corporation to eliminate the personal liability of directors of a corporation to
the corporation or its stockholders for monetary damages for a breach of
fiduciary duty as a director, except where the director breached his duty of
loyalty, failed to act in good faith, engaged in intentional misconduct or
knowingly violated a law, authorized the payment

                                        3

<PAGE>

of a dividend or approved a stock repurchase in violation of Delaware corporate
law or obtained an improper personal benefit. The Registrant has included such a
provision in its Certificate of Incorporation.

         Section 145 of the General Corporation Law of Delaware provides that a
corporation has the power to indemnify a director, officer, employee or agent of
the corporation and certain other persons serving at the request of the
corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which he is or is threatened to be
made a party by reason of such position, if such person shall have acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests of the corporation, and, in any criminal proceeding, if such person
had no reasonable cause to believe his conduct was unlawful; provided that, in
the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court determines that such indemnification is
proper under the circumstances.

         Article NINTH of the Registrant's Amended and Restated Certificate of
Incorporation provides that a director or officer of the Registrant (a) shall be
indemnified by the Registrant against all expenses (including attorneys' fees),
judgements, fines and amounts paid in settlement incurred in connection with any
litigation or other legal proceeding (other than an action by or in the right of
the Registrant) brought against him by virtue of his position as a director or
officer of the Registrant if he acted in good faith and in a manner he
reasonably believed to be in, or not opposed to, the best interest of the
registrant, and, with respect to any criminal action or proceeding, has no
reasonable cause to believe his conduct was unlawful and (b) shall be
indemnified by the Registrant against all expenses (including attorneys' fees),
judgment, fines and amounts paid in settlement incurred in connection with any
action by or in the right of the Registrant brought against him by virtue of his
position as a director or officer of the Registrant if he acted in good faith
and in a manner he reasonably believed to be in, or not opposed to, the best
interests of the Registrant, except that no indemnification shall be made with
respect to any matter as to which such person shall have been adjudged to be
liable to the Registrants, unless a court determines that, despite such
adjudication but in view of all of the circumstances, he is entitled to
indemnification of such expenses. Notwithstanding the foregoing, to the extent
that a director or officer has been successful, on the merits or otherwise,
including, without limitation, the dismissal of an action without prejudice, he
is required to be indemnified by the Registrant against all expenses (including
attorneys' fees) incurred in connection therewith. Expenses shall be advanced to
a Director or officer at his request, provided that he undertakes to repay the
amount advanced if it is ultimately determined that he is not entitled to
indemnification for such expenses.

         Indemnification is required to be made promptly unless the Registrant
determines that the applicable standard of conduct required for indemnification
has not been met. In the event the Registrant denies a request for
indemnification, or if the Registrant fails to dispose of a request for
indemnification within 60 days after such payment is claimed by the indemnitee,
such person is permitted to petition the court to make an independent
determination as to whether such person is entitled to indemnification. As a
condition precedent to the right of indemnification, the director or officer
must give the Registrant notice of the action for which indemnity is sought and
the Registrant has the right to participate in such action or assume the defense
thereof.

         Article NINTH of the Registrant's Amended and Restated Certificate of
Incorporation further provides that the indemnification provided herein is not
exclusive.

         Item 7.    EXEMPTION FROM REGISTRATION CLAIMED

              Not applicable.

                                        4

<PAGE>

         Item 8.    EXHIBITS

<TABLE>
<CAPTION>

Exhibit
Number               Description
----------           --------------
<S>                <C>
4.1 (1)              Amended and Restated Certificate of
                     Incorporation of the Registrant

4.2 (1)              Amended and Restated By-Laws of the Registrant

4.3 (2)              Specimen certificate for shares of Common Stock

5.1                  Opinion of Hale and Dorr LLP

23.1                 Consent of Hale and Dorr LLP (included in Exhibit 5.1)

23.2                 Consent of Ernst & Young LLP

24.1                 Power of Attorney (included on signature page
                     to this Registration Statement)

</TABLE>

------
(1)      Incorporated herein by reference from the Registrant's Quarterly Report
         on Form 10-Q, filed June 20, 1996 (File No. 0-28494).

(2)      Incorporated herein by reference from the Registrant's Registration
         Statement on Form S-1 (File No. 333-02490).

         Item 9.    UNDERTAKINGS

         1.   The 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;

                    (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; and

                    (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;

         PROVIDED, HOWEVER, that paragraphs (i) and (ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed with or furnished to the
Commission by the Registrant pursuant to Section 13 or Section 15(d) of the
Exchange Act that are incorporated by reference in the Registration Statement.

              (2) That, for the purpose of determining any liability under the
         Securities Act, each such post-effective amendment shall be deemed to
         be a new registration statement relating to the

                                        5

<PAGE>

         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.

         2. The Registrant hereby undertakes that, for purposes of determining
any liability under the Securities Act, each filing of the Registrant's annual
report pursuant to Section 13(a) or Section 15(d) of the Exchange Act that is
incorporated by reference in the 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.

         3. Insofar as indemnification for liabilities arising under the
Securities Act 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 Commission such
indemnification is against public policy as expressed in the Securities Act 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 and will be governed by the final
adjudication of such issue.

                                        6

<PAGE>

                                   SIGNATURES

         Pursuant to the requirements of the Securities Act, 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 this
21st day of December, 1999.

                                          MILLENNIUM PHARMACEUTICALS, INC.

                                          By:  /s/ MARK J. LEVIN
                                             ----------------------------------
                                          Name:    Mark J. Levin
                                          Title:   Chief Executive Officer

                        SIGNATURES AND POWER OF ATTORNEY

     We, the undersigned officers and directors of Millennium Pharmaceuticals,
Inc., hereby severally constitute and appoint Mark J. Levin, Kevin P. Starr and
John B. Douglas III, and each of them singly, our true and lawful attorneys with
full power to any of them, and to each of them singly, to sign for us and in our
names in the capacities indicated below the Registration Statement on Form S-8
filed herewith and any and all pre-effective and post-effective amendments to
said Registration Statement and generally to do all such things in our name and
behalf in our capacities as officers and directors to enable Millennium
Pharmaceuticals, Inc. to comply with the provisions of the Securities Act of
1933 and all requirements of the Securities and Exchange Commission, hereby
ratifying and confirming our signatures as they may be signed by our said
attorneys, or any of them, to said Registration Statement and any and all
amendments thereto.

     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 date indicated.

<TABLE>
<CAPTION>

             SIGNATURE                               TITLE                                  DATE
             ---------                               -----                                  ----
<S>                                   <C>                                           <C>
 /s/ Mark J. Levin                     Chief Executive Officer and Director           December  21, 1999
-------------------------------------  (Principal Executive Officer)
  Mark J. Levin

 /s/ Kevin P. Starr                    Chief Financial Officer (Principal             December  21, 1999
-------------------------------------  Financial and Accounting Officer)
  Kevin P. Starr

 /s/ Joshua Boger                      Director                                       December 21, 1999
-------------------------------------
  Joshua Boger, Ph.D.

 /s/ Eugene Cordes                     Director                                       December 21, 1999
-------------------------------------
  Eugene Cordes

</TABLE>

                                        7

<PAGE>

<TABLE>
<CAPTION>

<S>                                   <C>                                           <C>
 /s/ A. Grant Heidrich III             Director                                       December  21, 1999
-------------------------------------
  A. Grant Heidrich III

 /s/ Raju S. Kucherlapati              Director                                       December  21, 1999
-------------------------------------
   Raju S. Kucherlapati

 /s/ Eric S. Lander                  Director                                         December 21, 1999
-------------------------------------
  Eric S. Lander

 /s/ Steven C. Wheelwright           Director                                         December 21, 1999
-------------------------------------
  Steven C. Wheelwright

</TABLE>

                                        8

<PAGE>

                                  EXHIBIT INDEX

                              ---------------------

<TABLE>
<CAPTION>

Exhibit
Number            Description
----------        --------------
<S>             <C>
4.1 (1)           Amended and Restated Certificate of
                  Incorporation of the Registrant

4.2 (1)           Amended and Restated By-Laws of the Registrant

4.3 (2)           Specimen certificate for shares of Common Stock

5.1               Opinion of Hale and Dorr LLP

23.1              Consent of Hale and Dorr LLP (included in Exhibit 5.1)

23.2              Consent of Ernst & Young LLP

24.1              Power of Attorney (included on the signature page
                  to this Registration Statement)

</TABLE>

------

(1)  Incorporated herein by reference from the Registrant's Quarterly Report on
     Form 10-Q, filed June 20, 1996 (File No. 0-28494).
(2)  Incorporated herein by reference from the Registrant's Registration
     Statement on Form S-1 (File No. 333-02490).

                                        9
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 21475}]
{"company-data": {"conformed-name": "MILLENNIUM PHARMACEUTICALS INC", "cik": "0001002637", "assigned-sic": "2834", "irs-number": "043177038", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-93249", "film-number": "99778382"}, "business-address": {"street1": "75 SIDNEY STREET", "city": "CAMBRIDGE", "state": "MA", "zip": "02139", "phone": "6176797000"}, "mail-address": {"street1": "640 MEMORIAL DR", "city": "CAMBRIDGE", "state": "MA", "zip": "02139"}}
As filed with the Securities and Exchange Commission
                              on December 21, 1999

                                                      Registration No. 333-_____

-------------------------------------------------------------------------------
-------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D. C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                        MILLENNIUM PHARMACEUTICALS, INC.
             (Exact name of registrant as specified in its charter)

            DELAWARE                                         04-3177038
(State or other jurisdiction of                          (I.R.S. Employer
 incorporation or organization)                        Identification Number)

     75 SIDNEY STREET, CAMBRIDGE, MASSACHUSETTS                02139
      (Address of Principal Executive Offices)              (Zip Code)

          MILLENNIUM BIOTHERAPEUTICS, INC. 1997 EQUITY INCENTIVE PLAN
                            (Full title of the Plan)

                                  MARK J. LEVIN
                             CHIEF EXECUTIVE OFFICER
                        MILLENNIUM PHARMACEUTICALS, INC.
                                75 SIDNEY STREET
                         CAMBRIDGE, MASSACHUSETTS 02139

                                 WITH A COPY TO:

       David E. Redlick, Esq.                   John B. Douglas III, Esq.
       Kenneth A. Hoxsie, Esq.                        General Counsel
         Hale and Dorr LLP                   Millennium Pharmaceuticals, Inc.
         60 State Street                            75 Sidney Street
   Boston, Massachusetts 02109               Cambridge, Massachusetts 02139
         (617) 526-6000                             (617) 679-7000

            (Name, address, including zip code, and telephone number,
                   including area code, of agents for service)

                         CALCULATION OF REGISTRATION FEE
Proposed                Proposed
Title of                                         Maximum                 Maximum                  Amount of
Securities               Amount to be            Offering Price          Aggregate                Registration
to be Registered         Registered              Per Share               Offering Price           Fee
----------------         ------------            --------------          --------------           ------------
Common Stock,
$.001 par value          321,000 shares          101.00 (1)              32,421,000 (1)           $ 8,560
(1)  Estimated solely for the purpose of calculating the registration fee, and
     based upon the average of the high and low prices of the Common Stock on
     the Nasdaq National Market on December 17, 1999 in accordance with Rules
     457(c) and 457(h) of the Securities Act of 1933.

-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
EXPLANATORY NOTE

         This Registration Statement on Form S-8 is being filed to register the
shares of Common Stock of Millennium Pharmaceuticals, Inc. (the "Company" or
"Registrant") issuable pursuant to the Millennium BioTherapeutics, Inc. 1997
Equity Incentive Plan (the "Plan"). On December 21, 1999, pursuant to the terms
of Section 1.9 of the Agreement and Plan of Merger dated as of October 14, 1999
by and between the Company and Millennium BioTherapeutics, Inc. ("Millennium
BioTherapeutics"), the Company assumed the Plan and all of the outstanding
options to purchase Common Stock of Millennium BioTherapeutics issued under the
Plan.

                                        2
PART I.       INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

              The information required by Part I is included in documents sent
or given to participants in the Plan pursuant to Rule 428(b)(1) of the
Securities Act of 1933, as amended (the "Securities Act").

PART II.      INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

         Item 3.    INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

              The following documents, which are filed with the Securities and
Exchange Commission (the "Commission"), are incorporated in this Registration
Statement by reference:

              (1) The Registrant's latest annual report filed pursuant to
         Sections 13(a) or 15(d) of the Securities Exchange Act of 1934, as
         amended (the "Exchange Act"), or the latest prospectus filed pursuant
         to Rule 424(b) under the Securities Act that contains audited financial
         statements for the Registrant's latest fiscal year for which such
         statements have been filed.

              (2) All other reports filed pursuant to Sections 13(a) or 15(d) of
         the Exchange Act since the end of the fiscal year covered by the annual
         report or the prospectus referred to in (1) above.

              (3) The description of the common stock of the Registrant, $.001
         par value per share (the "Common Stock"), contained in the Registrant's
         Registration Statement on Form 8-A filed under the Exchange Act,
         including any amendment or report filed for the purpose of updating
         such description.

              All documents subsequently filed by the Registrant 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 shares of Common Stock
offered hereby have been sold or which deregisters all shares of Common Stock
then remaining unsold, shall be deemed to be incorporated by reference herein
and to be part hereof from the date of the filing of such documents. Any
statement contained in a document incorporated or deemed to be incorporated by
reference herein shall be deemed to be modified or superseded for purposes of
this Registration Statement to the extent that a statement contained herein or
in any other subsequently filed document which also is or is deemed to be
incorporated by reference herein modifies or supersedes such statement. Any
statement so modified or superseded shall be deemed, except as so modified or
superseded, to constitute a part of this Registration Statement.

         Item 4.    DESCRIPTION OF SECURITIES

              Not applicable.

         Item 5.    INTERESTS OF NAMED EXPERTS AND COUNSEL

              Not Applicable.

         Item 6.    INDEMNIFICATION OF DIRECTORS AND OFFICERS

              Section 102 of the Delaware General Corporation Law allows a
corporation to eliminate the personal liability of directors of a corporation to
the corporation or its stockholders for monetary damages for a breach of
fiduciary duty as a director, except where the director breached his duty of
loyalty, failed to act in good faith, engaged in intentional misconduct or
knowingly violated a law, authorized the payment

                                        3
of a dividend or approved a stock repurchase in violation of Delaware corporate
law or obtained an improper personal benefit. The Registrant has included such a
provision in its Certificate of Incorporation.

         Section 145 of the General Corporation Law of Delaware provides that a
corporation has the power to indemnify a director, officer, employee or agent of
the corporation and certain other persons serving at the request of the
corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which he is or is threatened to be
made a party by reason of such position, if such person shall have acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests of the corporation, and, in any criminal proceeding, if such person
had no reasonable cause to believe his conduct was unlawful; provided that, in
the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court determines that such indemnification is
proper under the circumstances.

         Article NINTH of the Registrant's Amended and Restated Certificate of
Incorporation provides that a director or officer of the Registrant (a) shall be
indemnified by the Registrant against all expenses (including attorneys' fees),
judgements, fines and amounts paid in settlement incurred in connection with any
litigation or other legal proceeding (other than an action by or in the right of
the Registrant) brought against him by virtue of his position as a director or
officer of the Registrant if he acted in good faith and in a manner he
reasonably believed to be in, or not opposed to, the best interest of the
registrant, and, with respect to any criminal action or proceeding, has no
reasonable cause to believe his conduct was unlawful and (b) shall be
indemnified by the Registrant against all expenses (including attorneys' fees),
judgment, fines and amounts paid in settlement incurred in connection with any
action by or in the right of the Registrant brought against him by virtue of his
position as a director or officer of the Registrant if he acted in good faith
and in a manner he reasonably believed to be in, or not opposed to, the best
interests of the Registrant, except that no indemnification shall be made with
respect to any matter as to which such person shall have been adjudged to be
liable to the Registrants, unless a court determines that, despite such
adjudication but in view of all of the circumstances, he is entitled to
indemnification of such expenses. Notwithstanding the foregoing, to the extent
that a director or officer has been successful, on the merits or otherwise,
including, without limitation, the dismissal of an action without prejudice, he
is required to be indemnified by the Registrant against all expenses (including
attorneys' fees) incurred in connection therewith. Expenses shall be advanced to
a Director or officer at his request, provided that he undertakes to repay the
amount advanced if it is ultimately determined that he is not entitled to
indemnification for such expenses.

         Indemnification is required to be made promptly unless the Registrant
determines that the applicable standard of conduct required for indemnification
has not been met. In the event the Registrant denies a request for
indemnification, or if the Registrant fails to dispose of a request for
indemnification within 60 days after such payment is claimed by the indemnitee,
such person is permitted to petition the court to make an independent
determination as to whether such person is entitled to indemnification. As a
condition precedent to the right of indemnification, the director or officer
must give the Registrant notice of the action for which indemnity is sought and
the Registrant has the right to participate in such action or assume the defense
thereof.

         Article NINTH of the Registrant's Amended and Restated Certificate of
Incorporation further provides that the indemnification provided herein is not
exclusive.

         Item 7.    EXEMPTION FROM REGISTRATION CLAIMED

              Not applicable.

                                        4
Item 8.    EXHIBITS
Exhibit
Number               Description
----------           --------------
4.1 (1)              Amended and Restated Certificate of
                     Incorporation of the Registrant

4.2 (1)              Amended and Restated By-Laws of the Registrant

4.3 (2)              Specimen certificate for shares of Common Stock

5.1                  Opinion of Hale and Dorr LLP

23.1                 Consent of Hale and Dorr LLP (included in Exhibit 5.1)

23.2                 Consent of Ernst & Young LLP

24.1                 Power of Attorney (included on signature page
                     to this Registration Statement)
------
(1)      Incorporated herein by reference from the Registrant's Quarterly Report
         on Form 10-Q, filed June 20, 1996 (File No. 0-28494).

(2)      Incorporated herein by reference from the Registrant's Registration
         Statement on Form S-1 (File No. 333-02490).

         Item 9.    UNDERTAKINGS

         1.   The 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;

                    (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; and

                    (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;

         PROVIDED, HOWEVER, that paragraphs (i) and (ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed with or furnished to the
Commission by the Registrant pursuant to Section 13 or Section 15(d) of the
Exchange Act that are incorporated by reference in the Registration Statement.

              (2) That, for the purpose of determining any liability under the
         Securities Act, each such post-effective amendment shall be deemed to
         be a new registration statement relating to the

                                        5
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.

         2. The Registrant hereby undertakes that, for purposes of determining
any liability under the Securities Act, each filing of the Registrant's annual
report pursuant to Section 13(a) or Section 15(d) of the Exchange Act that is
incorporated by reference in the 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.

         3. Insofar as indemnification for liabilities arising under the
Securities Act 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 Commission such
indemnification is against public policy as expressed in the Securities Act 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 and will be governed by the final
adjudication of such issue.

                                        6
SIGNATURES

         Pursuant to the requirements of the Securities Act, 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 this
21st day of December, 1999.

                                          MILLENNIUM PHARMACEUTICALS, INC.

                                          By:  /s/ MARK J. LEVIN
                                             ----------------------------------
                                          Name:    Mark J. Levin
                                          Title:   Chief Executive Officer

                        SIGNATURES AND POWER OF ATTORNEY

     We, the undersigned officers and directors of Millennium Pharmaceuticals,
Inc., hereby severally constitute and appoint Mark J. Levin, Kevin P. Starr and
John B. Douglas III, and each of them singly, our true and lawful attorneys with
full power to any of them, and to each of them singly, to sign for us and in our
names in the capacities indicated below the Registration Statement on Form S-8
filed herewith and any and all pre-effective and post-effective amendments to
said Registration Statement and generally to do all such things in our name and
behalf in our capacities as officers and directors to enable Millennium
Pharmaceuticals, Inc. to comply with the provisions of the Securities Act of
1933 and all requirements of the Securities and Exchange Commission, hereby
ratifying and confirming our signatures as they may be signed by our said
attorneys, or any of them, to said Registration Statement and any and all
amendments thereto.

     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 date indicated.
SIGNATURE                               TITLE                                  DATE
             ---------                               -----                                  ----
/s/ Mark J. Levin                     Chief Executive Officer and Director           December  21, 1999
-------------------------------------  (Principal Executive Officer)
  Mark J. Levin

 /s/ Kevin P. Starr                    Chief Financial Officer (Principal             December  21, 1999
-------------------------------------  Financial and Accounting Officer)
  Kevin P. Starr

 /s/ Joshua Boger                      Director                                       December 21, 1999
-------------------------------------
  Joshua Boger, Ph.D.

 /s/ Eugene Cordes                     Director                                       December 21, 1999
-------------------------------------
  Eugene Cordes
7
/s/ A. Grant Heidrich III             Director                                       December  21, 1999
-------------------------------------
  A. Grant Heidrich III

 /s/ Raju S. Kucherlapati              Director                                       December  21, 1999
-------------------------------------
   Raju S. Kucherlapati

 /s/ Eric S. Lander                  Director                                         December 21, 1999
-------------------------------------
  Eric S. Lander

 /s/ Steven C. Wheelwright           Director                                         December 21, 1999
-------------------------------------
  Steven C. Wheelwright
8
EXHIBIT INDEX

                              ---------------------
Exhibit
Number            Description
----------        --------------
4.1 (1)           Amended and Restated Certificate of
                  Incorporation of the Registrant

4.2 (1)           Amended and Restated By-Laws of the Registrant

4.3 (2)           Specimen certificate for shares of Common Stock

5.1               Opinion of Hale and Dorr LLP

23.1              Consent of Hale and Dorr LLP (included in Exhibit 5.1)

23.2              Consent of Ernst & Young LLP

24.1              Power of Attorney (included on the signature page
                  to this Registration Statement)
------

(1)  Incorporated herein by reference from the Registrant's Quarterly Report on
     Form 10-Q, filed June 20, 1996 (File No. 0-28494).
(2)  Incorporated herein by reference from the Registrant's Registration
     Statement on Form S-1 (File No. 333-02490).

                                        9