As filed with the Securities and Exchange Commission on July 6, 2004
                                                   Registration No. 333-
===============================================================================

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933



                          Momenta Pharmaceuticals, Inc.
             (Exact Name of Registrant as Specified in Its Charter)

                 Delaware                                    04-3561634
  (State or Other Jurisdiction of Incorporation           (I.R.S. Employer
              or  Organization)                          Identification No.)

             43 Moulton Street                                    02138
                Cambridge, MA
    (Address of Principal Executive Offices)                   (Zip Code)

                            2002 Stock Incentive Plan
                            2004 Stock Incentive Plan
                        2004 Employee Stock Purchase Plan
                            (Full Title of the Plans)

                                  Alan L. Crane
          Chairman of the Board, President and Chief Executive Officer
                          Momenta Pharmaceuticals, Inc.
                                43 Moulton Street
                               Cambridge, MA 02138
                     (Name and Address of Agent For Service)

                                 (617) 491-9700
          (Telephone Number, Including Area Code, of Agent For Service)

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
========================================================================================================================
                                                                         Proposed
                                                                          Maximum       Proposed Maximum     Amount of
                                                      Amount to be    Offering Price        Aggregate       Registration
       Title of Securities to be Registered           Registered(1)      Per Share       Offering Price         Fee
-------------------------------------------------------------------------------------------------------------------------
Common Stock, par value $0.0001 per share:

<S>                                                     <C>               <C>             <C>                   <C>
 Shares to be issued pursuant to prior option
    grants under the 2002 Stock Incentive Plan ....     1,180,420         $0.81(3)        $956,140.20(3)        $121.14

 Shares issuable pursuant to future option grants
    and purchases under the 2004 Stock Incentive
    Plan and the 2004 Employee Stock Purchase Plan.     4,473,437         $8.55(4)       $38,247,886.35(4)    $4,846.00
------------------------------------------------------------------------------------------------------------------------
       TOTAL.......................................   5,653,857(2)                       $39,204,026.55       $4,967.14
========================================================================================================================
</TABLE>

(1)  In accordance  with Rule 416 under the  Securities Act of 1933, as amended,
     this  registration  statement  shall  be  deemed  to cover  any  additional
     securities  that may from time to time be  offered  or  issued  to  prevent
     dilution   resulting  from  stock  splits,   stock   dividends  or  similar
     transactions.

(2)  Consists of (i) 1,180,420  shares  issuable under the 2002 Stock  Incentive
     Plan,  (ii) 3,948,785  shares issuable under the 2004 Stock Incentive Plan,
     and (iii) 524,652  shares  issuable  under the 2004 Employee Stock Purchase
     Plan.

(3)  Estimated  solely for the purpose of calculating  the  registration  fee in
     accordance with Rule 457(h) of the Securities Act of 1933, as amended.  The
     price per share and aggregate offering price are calculated on the basis of
     $0.79, the weighted

<PAGE>

     average exercise price of the 1,180,420 shares subject to outstanding stock
     option grants under the 2002 Stock  Incentive  Plan, at prices ranging from
     $0.08 to $4.91.

(4)  Estimated  solely  for the  purpose of  calculating  the  registration  fee
     pursuant  to Rules  457(c) and  457(h) of the  Securities  Act of 1933,  as
     amended,  and  based  upon the  average  of the high and low  prices of the
     registrant's Common Stock as reported on the Nasdaq National Market on June
     30, 2004.

================================================================================

<PAGE>

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

Item 1.  Plan Information.

     The  information  required by Item 1 is included in documents sent or given
to participants in the plans covered by this registration  statement pursuant to
Rule 428(b)(1) of the Securities Act of 1933, as amended (the "Securities Act").

Item 2.  Registrant Information and Employee Plan Annual Information.

     The written  statement  required by Item 2 is included in documents sent or
given to  participants  in the  plans  covered  by this  registration  statement
pursuant to Rule 428(b)(1) of the Securities Act.

                                    PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  Incorporation of Documents by Reference.

     The registrant is subject to the informational  and reporting  requirements
of Sections  13(a),  14, and 15(d) of the  Securities  Exchange Act of 1934,  as
amended (the "Exchange Act"), and in accordance  therewith files reports,  proxy
statements and other  information  with the  Securities and Exchange  Commission
(the  "Commission").  The  following  documents,  which  are on  file  with  the
Commission, are incorporated in this registration statement by reference:

     (a) The  registrant's  latest annual report filed pursuant to Section 13(a)
or 15(d) of 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.

     (b) All other  reports  filed  pursuant  to  Section  13(a) or 15(d) of the
Exchange Act since the end of the fiscal year  covered by the document  referred
to in (a) above.

     (c)  The  description  of the  securities  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 securities offered hereby have
been sold or which  deregisters all securities then remaining  unsold,  shall be
deemed to be incorporated by reference in this registration  statement 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 the  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 not be deemed, except as so modified or superseded,
to constitute a part of this registration statement.

Item 4.  Description of Securities.

     Not applicable.

                                      -1-

<PAGE>

Item 5.  Interests of Named Experts and Counsel.

     Wilmer Cutler  Pickering Hale and Dorr LLP has opined as to the legality of
the securities being offered by this registration statement.

Item 6.  Indemnification of Directors and Officers.

     Section 102 of the General Corporation Law of the State of Delaware permits
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 of a dividend or approved a
stock repurchase in violation of Delaware  corporate law or obtained an improper
personal benefit. The registrant's certificate of incorporation provides that no
director of the registrant  shall be personally  liable to the registrant or its
stockholders  for  monetary  damages  for  any  breach  of  fiduciary  duty as a
director,  notwithstanding any provision of law imposing such liability,  except
to the  extent  that  the  General  Corporation  Law of the  State  of  Delaware
prohibits the  elimination  or limitation of liability of directors for breaches
of fiduciary duty.

     Section  145 of the  General  Corporation  Law of  the  State  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  expenses  (including
attorneys' fees), judgments,  fines and amounts paid in settlements actually and
reasonably  incurred  by the  person  in  connection  with  an  action,  suit or
proceeding  to which he is or is threatened to be made a party by reason of such
position,  if such  person  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  action or  proceeding,  had no reasonable  cause to believe his
conduct was unlawful,  except that, in the case of actions  brought by or in the
right of the corporation,  no indemnification  shall be made with respect to any
claim,  issue or matter as to which such person  shall have been  adjudged to be
liable  to the  corporation  unless  and only to the  extent  that the  Court of
Chancery or other  adjudicating  court determines that, despite the adjudication
of liability but in view of all of the circumstances of the case, such person is
fairly and reasonably entitled to indemnity for such expenses which the Court of
Chancery or such other court shall deem proper.

     The registrant's  certificate of incorporation provides that the registrant
will  indemnify  each  person who was or is a party or  threatened  to be made a
party to any threatened,  pending or completed action, suit or proceeding (other
than an action by or in the right of the corporation) by reason of the fact that
he or she is or was,  or has  agreed to  become,  a  director  or officer of the
registrant,  or is or was serving,  or has agreed to serve, at the  registrant's
request as a director, officer, partner, employee or trustee of, or in a similar
capacity with, another corporation,  partnership,  joint venture, trust or other
enterprise (all such persons being referred to as an "Indemnitee"), or by reason
of any action  alleged to have been taken or omitted in such  capacity,  against
all expenses (including attorneys' fees),  judgments,  fines and amounts paid in
settlement actually and reasonably incurred in connection with such action, suit
or proceeding and any appeal therefrom,  if such Indedmnitee acted in good faith
and in a manner he or she  reasonably  believed to be in, or not opposed to, the
corporation's  best  interests,  and,  with  respect to any  criminal  action or
proceeding,  he or she had no reasonable cause to believe his or her conduct was
unlawful.  The  registrant's  certificate  of  incorporation  provides  that the
registrant  will  indemnify any Indemnitee who was or in a party to an action or
suit by or in the right of the corporation to procure a judgment in its favor by
reason of the fact that the  Indemnitee  is or was,  or has agreed to become,  a
director or officer of the  registrant,  or is or was serving,  or has agreed to
serve, at the registrant's request as a director,  officer, partner, employee or
trustee of, or in a similar  capacity with,  another  corporation,  partnership,
joint venture, trust or other enterprise,  or by reason of any action alleged to
have been taken or omitted in such  capacity,  against all  expenses  (including
attorneys' fees) and, to the extent permitted by

                                      -2-

<PAGE>

law, amounts paid in settlement  actually and reasonably  incurred in connection
with  such  action,  suit  or  proceeding,  and  any  appeal  therefrom,  if the
Indemnitee acted in good faith and in a manner he or she reasonably  believed to
be in, or not opposed to, the best interests of the corporation,  except that no
indemnification  shall be made with respect to any claim,  issue or matter as to
which such  person  shall  have been  adjudged  to be liable to the  registrant,
unless a court determines that,  despite such adjudication but in view of all of
the  circumstances,  he or she is entitled to  indemnification of such expenses.
Notwithstanding  the  foregoing,  to the  extent  that any  Indemnitee  has been
successful,  on the merits or otherwise,  he or she will be  indemnified  by the
registrant  against  all  expenses  (including  attorneys'  fees)  actually  and
reasonably  incurred in  connection  therewith.  Expenses must be advanced to an
Indemnitee under certain circumstances.

     The indemnification provisions contained in the registrant's certificate of
incorporation  are not  exclusive  of any other  rights to which a person may be
entitled by law, agreement,  vote of stockholders or disinterested  directors or
otherwise.

     In addition,  the registrant maintains insurance on behalf of its directors
and executive officers insuring them against any liability asserted against them
in their capacities as directors or officers or arising out of such status.

Item 7.  Exemption from Registration Claimed.

     Not applicable.

Item 8.  Exhibits.

     The Exhibit Index immediately preceding the exhibits is incorporated herein
by reference.

Item 9.  Undertakings.

     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;

          (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.

                                      -3-
<PAGE>

(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 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.

     The  undersigned   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.

     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 Securities  and Exchange  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.

                                      -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 this 6th
day of July, 2004.

                             MOMENTA PHARMACEUTICALS, INC.


                             By: /s/ Alan L. Crane
                                 ------------------
                                 Alan L. Crane
                                 Chairman, President and Chief Executive Officer

                        POWER OF ATTORNEY AND SIGNATURES

     We, the  undersigned  officers and  directors  of Momenta  Pharmaceuticals,
Inc., hereby severally constitute and appoint Alan L. Crane and Richard P. Shea,
and each of them singly,  our true and lawful attorneys with full power to them,
and  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 subsequent amendments to said registration  statement,  and generally to
do all such things in our names and on our behalf in our  capacities as officers
and  directors  to enable  Momenta  Pharmaceuticals,  Inc.  to  comply  with the
provisions of the Securities Act of 1933, as amended,  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 dates indicated.

<TABLE>
<CAPTION>
                Signature                               Title                                        Date
                ---------                               -----                                        ----
<S>         <C>                             <C>                                                    <C>
            /s/ Alan L. Crane
     --------------------------------       Chairman, President, Chief Executive                   July 6, 2004
              Alan L. Crane                 Officer and Director (Principal Executive
                                            Officer)

           /s/ Richard P. Shea
     --------------------------------       Chief Financial Officer                                July 6, 2004
             Richard P. Shea                (Principal Financial and Accounting Officer)

         /s/ Peter Barrett, Ph.D.
     ---------------------------------      Director                                               July 6, 2004
           Peter Barrett, Ph.D.

            /s/ John K. Clarke
     ---------------------------------      Director                                               July 6, 2004
              John K. Clarke

   /s/ Peter Barton Hutt, LL.B., LL.M.
  ------------------------------------      Director                                               July 6, 2004
     Peter Barton Hutt, LL.B., LL.M.

     /s/ Robert S. Langer, Jr., Sc.D.
     ---------------------------------      Director                                               July 6, 2004
       Robert S. Langer, Jr., Sc.D.


    ----------------------------------      Director
      Stephen T. Reeders, D.M., MRCP


     ---------------------------------      Director
         Ram Sasisekharan, Ph.D.


<PAGE>

       /s/ Bennett M. Shapiro, M.D.
     ---------------------------------       Director                                               July 6, 2004
         Bennett M. Shapiro, M.D.


  /s/ Christoph H. Westphal, M.D., Ph.D.
   -------------------------------------     Director                                               July 6, 2004
    Christoph H. Westphal, M.D., Ph.D.

       /s/ John L. Zabriskie, Ph.D.
   -------------------------------------     Director                                               July 6, 2004
         John L. Zabriskie, Ph.D.
</TABLE>




<PAGE>


                                INDEX TO EXHIBITS

Number        Description
------        -----------

4.1(1)        Third Amended and Restated Certificate of Incorporation
              of the Registrant

4.2(1)        Second Amended and Restated Bylaws of the Registrant

5             Opinion of Wilmer Cutler Pickering Hale and Dorr LLP, counsel to
              the Registrant

23.1          Consent of Wilmer Cutler Pickering Hale and Dorr LLP (included in
              Exhibit 5)

23.2          Consent of Ernst & Young LLP

24.1          Power of Attorney (included on the signature page)


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

(1)  Previously filed with the Securities and Exchange  Commission as an Exhibit
     to the  Registrant's  Registration  Statement on Form S-1, as amended (File
     No. 333-113522) and incorporated herein by reference.
[{"type": "S-8", "sequence": "1", "filename": "forms8_7104.txt", "description": "FORM S-8", "secsgml_size_bytes": 23524}]
{"company-data": {"conformed-name": "MOMENTA PHARMACEUTICALS INC", "cik": "0001235010", "assigned-sic": "2836", "irs-number": "043561634", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-117173", "film-number": "04902787"}, "business-address": {"street1": "43 MOULTON STREET", "city": "CAMBRIDGE", "state": "MA", "zip": "02138", "phone": "6174919700"}}
As filed with the Securities and Exchange Commission on July 6, 2004
                                                   Registration No. 333-
===============================================================================

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                          Momenta Pharmaceuticals, Inc.
             (Exact Name of Registrant as Specified in Its Charter)

                 Delaware                                    04-3561634
  (State or Other Jurisdiction of Incorporation           (I.R.S. Employer
              or  Organization)                          Identification No.)

             43 Moulton Street                                    02138
                Cambridge, MA
    (Address of Principal Executive Offices)                   (Zip Code)

                            2002 Stock Incentive Plan
                            2004 Stock Incentive Plan
                        2004 Employee Stock Purchase Plan
                            (Full Title of the Plans)

                                  Alan L. Crane
          Chairman of the Board, President and Chief Executive Officer
                          Momenta Pharmaceuticals, Inc.
                                43 Moulton Street
                               Cambridge, MA 02138
                     (Name and Address of Agent For Service)

                                 (617) 491-9700
          (Telephone Number, Including Area Code, of Agent For Service)

                         CALCULATION OF REGISTRATION FEE
========================================================================================================================
                                                                         Proposed
                                                                          Maximum       Proposed Maximum     Amount of
                                                      Amount to be    Offering Price        Aggregate       Registration
       Title of Securities to be Registered           Registered(1)      Per Share       Offering Price         Fee
-------------------------------------------------------------------------------------------------------------------------
Common Stock, par value $0.0001 per share:
Shares to be issued pursuant to prior option
    grants under the 2002 Stock Incentive Plan ....     1,180,420         $0.81(3)        $956,140.20(3)        $121.14

 Shares issuable pursuant to future option grants
    and purchases under the 2004 Stock Incentive
    Plan and the 2004 Employee Stock Purchase Plan.     4,473,437         $8.55(4)       $38,247,886.35(4)    $4,846.00
------------------------------------------------------------------------------------------------------------------------
       TOTAL.......................................   5,653,857(2)                       $39,204,026.55       $4,967.14
========================================================================================================================
(1)  In accordance  with Rule 416 under the  Securities Act of 1933, as amended,
     this  registration  statement  shall  be  deemed  to cover  any  additional
     securities  that may from time to time be  offered  or  issued  to  prevent
     dilution   resulting  from  stock  splits,   stock   dividends  or  similar
     transactions.

(2)  Consists of (i) 1,180,420  shares  issuable under the 2002 Stock  Incentive
     Plan,  (ii) 3,948,785  shares issuable under the 2004 Stock Incentive Plan,
     and (iii) 524,652  shares  issuable  under the 2004 Employee Stock Purchase
     Plan.

(3)  Estimated  solely for the purpose of calculating  the  registration  fee in
     accordance with Rule 457(h) of the Securities Act of 1933, as amended.  The
     price per share and aggregate offering price are calculated on the basis of
     $0.79, the weighted
average exercise price of the 1,180,420 shares subject to outstanding stock
     option grants under the 2002 Stock  Incentive  Plan, at prices ranging from
     $0.08 to $4.91.

(4)  Estimated  solely  for the  purpose of  calculating  the  registration  fee
     pursuant  to Rules  457(c) and  457(h) of the  Securities  Act of 1933,  as
     amended,  and  based  upon the  average  of the high and low  prices of the
     registrant's Common Stock as reported on the Nasdaq National Market on June
     30, 2004.

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

Item 1.  Plan Information.

     The  information  required by Item 1 is included in documents sent or given
to participants in the plans covered by this registration  statement pursuant to
Rule 428(b)(1) of the Securities Act of 1933, as amended (the "Securities Act").

Item 2.  Registrant Information and Employee Plan Annual Information.

     The written  statement  required by Item 2 is included in documents sent or
given to  participants  in the  plans  covered  by this  registration  statement
pursuant to Rule 428(b)(1) of the Securities Act.

                                    PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  Incorporation of Documents by Reference.

     The registrant is subject to the informational  and reporting  requirements
of Sections  13(a),  14, and 15(d) of the  Securities  Exchange Act of 1934,  as
amended (the "Exchange Act"), and in accordance  therewith files reports,  proxy
statements and other  information  with the  Securities and Exchange  Commission
(the  "Commission").  The  following  documents,  which  are on  file  with  the
Commission, are incorporated in this registration statement by reference:

     (a) The  registrant's  latest annual report filed pursuant to Section 13(a)
or 15(d) of 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.

     (b) All other  reports  filed  pursuant  to  Section  13(a) or 15(d) of the
Exchange Act since the end of the fiscal year  covered by the document  referred
to in (a) above.

     (c)  The  description  of the  securities  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 securities offered hereby have
been sold or which  deregisters all securities then remaining  unsold,  shall be
deemed to be incorporated by reference in this registration  statement 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 the  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 not be deemed, except as so modified or superseded,
to constitute a part of this registration statement.

Item 4.  Description of Securities.

     Not applicable.

                                      -1-
Item 5.  Interests of Named Experts and Counsel.

     Wilmer Cutler  Pickering Hale and Dorr LLP has opined as to the legality of
the securities being offered by this registration statement.

Item 6.  Indemnification of Directors and Officers.

     Section 102 of the General Corporation Law of the State of Delaware permits
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 of a dividend or approved a
stock repurchase in violation of Delaware  corporate law or obtained an improper
personal benefit. The registrant's certificate of incorporation provides that no
director of the registrant  shall be personally  liable to the registrant or its
stockholders  for  monetary  damages  for  any  breach  of  fiduciary  duty as a
director,  notwithstanding any provision of law imposing such liability,  except
to the  extent  that  the  General  Corporation  Law of the  State  of  Delaware
prohibits the  elimination  or limitation of liability of directors for breaches
of fiduciary duty.

     Section  145 of the  General  Corporation  Law of  the  State  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  expenses  (including
attorneys' fees), judgments,  fines and amounts paid in settlements actually and
reasonably  incurred  by the  person  in  connection  with  an  action,  suit or
proceeding  to which he is or is threatened to be made a party by reason of such
position,  if such  person  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  action or  proceeding,  had no reasonable  cause to believe his
conduct was unlawful,  except that, in the case of actions  brought by or in the
right of the corporation,  no indemnification  shall be made with respect to any
claim,  issue or matter as to which such person  shall have been  adjudged to be
liable  to the  corporation  unless  and only to the  extent  that the  Court of
Chancery or other  adjudicating  court determines that, despite the adjudication
of liability but in view of all of the circumstances of the case, such person is
fairly and reasonably entitled to indemnity for such expenses which the Court of
Chancery or such other court shall deem proper.

     The registrant's  certificate of incorporation provides that the registrant
will  indemnify  each  person who was or is a party or  threatened  to be made a
party to any threatened,  pending or completed action, suit or proceeding (other
than an action by or in the right of the corporation) by reason of the fact that
he or she is or was,  or has  agreed to  become,  a  director  or officer of the
registrant,  or is or was serving,  or has agreed to serve, at the  registrant's
request as a director, officer, partner, employee or trustee of, or in a similar
capacity with, another corporation,  partnership,  joint venture, trust or other
enterprise (all such persons being referred to as an "Indemnitee"), or by reason
of any action  alleged to have been taken or omitted in such  capacity,  against
all expenses (including attorneys' fees),  judgments,  fines and amounts paid in
settlement actually and reasonably incurred in connection with such action, suit
or proceeding and any appeal therefrom,  if such Indedmnitee acted in good faith
and in a manner he or she  reasonably  believed to be in, or not opposed to, the
corporation's  best  interests,  and,  with  respect to any  criminal  action or
proceeding,  he or she had no reasonable cause to believe his or her conduct was
unlawful.  The  registrant's  certificate  of  incorporation  provides  that the
registrant  will  indemnify any Indemnitee who was or in a party to an action or
suit by or in the right of the corporation to procure a judgment in its favor by
reason of the fact that the  Indemnitee  is or was,  or has agreed to become,  a
director or officer of the  registrant,  or is or was serving,  or has agreed to
serve, at the registrant's request as a director,  officer, partner, employee or
trustee of, or in a similar  capacity with,  another  corporation,  partnership,
joint venture, trust or other enterprise,  or by reason of any action alleged to
have been taken or omitted in such  capacity,  against all  expenses  (including
attorneys' fees) and, to the extent permitted by

                                      -2-
law, amounts paid in settlement  actually and reasonably  incurred in connection
with  such  action,  suit  or  proceeding,  and  any  appeal  therefrom,  if the
Indemnitee acted in good faith and in a manner he or she reasonably  believed to
be in, or not opposed to, the best interests of the corporation,  except that no
indemnification  shall be made with respect to any claim,  issue or matter as to
which such  person  shall  have been  adjudged  to be liable to the  registrant,
unless a court determines that,  despite such adjudication but in view of all of
the  circumstances,  he or she is entitled to  indemnification of such expenses.
Notwithstanding  the  foregoing,  to the  extent  that any  Indemnitee  has been
successful,  on the merits or otherwise,  he or she will be  indemnified  by the
registrant  against  all  expenses  (including  attorneys'  fees)  actually  and
reasonably  incurred in  connection  therewith.  Expenses must be advanced to an
Indemnitee under certain circumstances.

     The indemnification provisions contained in the registrant's certificate of
incorporation  are not  exclusive  of any other  rights to which a person may be
entitled by law, agreement,  vote of stockholders or disinterested  directors or
otherwise.

     In addition,  the registrant maintains insurance on behalf of its directors
and executive officers insuring them against any liability asserted against them
in their capacities as directors or officers or arising out of such status.

Item 7.  Exemption from Registration Claimed.

     Not applicable.

Item 8.  Exhibits.

     The Exhibit Index immediately preceding the exhibits is incorporated herein
by reference.

Item 9.  Undertakings.

     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;

          (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.

                                      -3-
(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 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.

     The  undersigned   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.

     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 Securities  and Exchange  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.

                                      -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 this 6th
day of July, 2004.

                             MOMENTA PHARMACEUTICALS, INC.

                             By: /s/ Alan L. Crane
                                 ------------------
                                 Alan L. Crane
                                 Chairman, President and Chief Executive Officer

                        POWER OF ATTORNEY AND SIGNATURES

     We, the  undersigned  officers and  directors  of Momenta  Pharmaceuticals,
Inc., hereby severally constitute and appoint Alan L. Crane and Richard P. Shea,
and each of them singly,  our true and lawful attorneys with full power to them,
and  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 subsequent amendments to said registration  statement,  and generally to
do all such things in our names and on our behalf in our  capacities as officers
and  directors  to enable  Momenta  Pharmaceuticals,  Inc.  to  comply  with the
provisions of the Securities Act of 1933, as amended,  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 dates indicated.
Signature                               Title                                        Date
                ---------                               -----                                        ----
/s/ Alan L. Crane
     --------------------------------       Chairman, President, Chief Executive                   July 6, 2004
              Alan L. Crane                 Officer and Director (Principal Executive
                                            Officer)

           /s/ Richard P. Shea
     --------------------------------       Chief Financial Officer                                July 6, 2004
             Richard P. Shea                (Principal Financial and Accounting Officer)

         /s/ Peter Barrett, Ph.D.
     ---------------------------------      Director                                               July 6, 2004
           Peter Barrett, Ph.D.

            /s/ John K. Clarke
     ---------------------------------      Director                                               July 6, 2004
              John K. Clarke

   /s/ Peter Barton Hutt, LL.B., LL.M.
  ------------------------------------      Director                                               July 6, 2004
     Peter Barton Hutt, LL.B., LL.M.

     /s/ Robert S. Langer, Jr., Sc.D.
     ---------------------------------      Director                                               July 6, 2004
       Robert S. Langer, Jr., Sc.D.

    ----------------------------------      Director
      Stephen T. Reeders, D.M., MRCP

     ---------------------------------      Director
         Ram Sasisekharan, Ph.D.
/s/ Bennett M. Shapiro, M.D.
     ---------------------------------       Director                                               July 6, 2004
         Bennett M. Shapiro, M.D.

  /s/ Christoph H. Westphal, M.D., Ph.D.
   -------------------------------------     Director                                               July 6, 2004
    Christoph H. Westphal, M.D., Ph.D.

       /s/ John L. Zabriskie, Ph.D.
   -------------------------------------     Director                                               July 6, 2004
         John L. Zabriskie, Ph.D.
INDEX TO EXHIBITS

Number        Description
------        -----------

4.1(1)        Third Amended and Restated Certificate of Incorporation
              of the Registrant

4.2(1)        Second Amended and Restated Bylaws of the Registrant

5             Opinion of Wilmer Cutler Pickering Hale and Dorr LLP, counsel to
              the Registrant

23.1          Consent of Wilmer Cutler Pickering Hale and Dorr LLP (included in
              Exhibit 5)

23.2          Consent of Ernst & Young LLP

24.1          Power of Attorney (included on the signature page)

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

(1)  Previously filed with the Securities and Exchange  Commission as an Exhibit
     to the  Registrant's  Registration  Statement on Form S-1, as amended (File
     No. 333-113522) and incorporated herein by reference.