content: <PAGE>   1
       As filed with the Securities and Exchange Commission on August 31, 2000
                                                         Registration No. 333-____
  ================================================================================
  
                         SECURITIES AND EXCHANGE COMMISSION
                               WASHINGTON, D.C. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                                THE MEDICINES COMPANY
               (Exact Name of Registrant as Specified in Its Charter)
  
           DELAWARE                                        04-3324394
  (State or Other Jurisdiction of                       (I.R.S. Employer
  Incorporation or Organization)                       Identification No.)
  
  ONE CAMBRIDGE CENTER, CAMBRIDGE, MASSACHUSETTS             02142
  (Address of Principal Executive Offices)                 (Zip Code)
  
                              1998 STOCK INCENTIVE PLAN
                       2000 OUTSIDE DIRECTOR STOCK OPTION PLAN
                          2000 EMPLOYEE STOCK PURCHASE PLAN
                              (Full Title of the Plan)
  
                                  CLIVE A. MEANWELL
                               CHIEF EXECUTIVE OFFICER
                                THE MEDICINES COMPANY
                                ONE CAMBRIDGE CENTER
                           CAMBRIDGE, MASSACHUSETTS 02142
                       (Name and Address of Agent for Service)
                                   (617) 225-9099
            (Telephone number, Including Area Code, of Agent For Service)
  
                           CALCULATION OF REGISTRATION FEE
  <TABLE>
  <CAPTION>
  
  ================================================================================================================
  Title of Each Class                               Proposed Maximum       Proposed Maximum
  of Securities to                                 Offering Price Per     Aggregate Offering          Amount of
  be  Registered        Amount to be Registered           Share                  Price            Registration Fee
  ----------------------------------------------------------------------------------------------------------------
  <S>                <C>                        <C>                    <C>                    <C>
  Common Stock,
  $0.001 par value          4,873,759 shares           $18.938(1)           $92,299,248(1)           $24,367(1)
  per share
  ================================================================================================================
  </TABLE>
  
  (1)  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
       August 30, 2000.
  
  
  <PAGE>   2
  
  PART I. INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS
  
       ITEM 1. PLAN INFORMATION.
  
       The information required by Part I is included in documents sent or given
  to participants in the 1998 Stock Incentive Plan, the 2000 Outside Director
  Stock Option Plan and the 2000 Employee Stock Purchase Plan of The Medicines
  Company 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 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 Common Stock of the registrant, $0.01 par value
  per share (the "Common Stock"), contained in the registrant's registration
  statement on Form 8-A and 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 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.
  
  
  
                                        -2-
  <PAGE>   3
  
  
       ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.
  
       Hale and Dorr LLP has opined as to the legality of the securities being
  offered by this registration statement. Partners of Hale and Dorr LLP
  beneficially own an aggregate of 23,634 shares of Common Stock and a warrant to
  purchase an aggregate of 1,554 shares of Common Stock.
  
       ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.
  
       The Registrant's Third Amended and Restated Certificate of Incorporation,
  as amended to date (the "Charter") provides that, except to the extent
  prohibited by the Delaware General Corporation Law (the "DGCL"), the
  Registrant's directors shall not be personally liable to the Registrant or its
  stockholders for monetary damages for any breach of fiduciary duty as directors
  of the Registrant. Under the DGCL, the directors have a fiduciary duty to the
  Registrant which is not eliminated by this provision of the Charter and, in
  appropriate circumstances, equitable remedies such as injunctive or other forms
  of nonmonetary relief will remain available. In addition, each director will
  continue to be subject to liability under the DGCL for breach of the director's
  duty of loyalty to the Registrant, for acts or omissions which are found by a
  court of competent jurisdiction to be not in good faith or involving intentional
  misconduct, for knowing violations of law, for actions leading to improper
  personal benefit to the director, and for payment of dividends or approval of
  stock repurchases or redemptions that are prohibited by DGCL. This provision
  also does not affect the directors' responsibilities under any other laws, such
  as the Federal securities laws or state or Federal environmental laws. The
  Registrant has obtained liability insurance for its officers and directors.
  
       Section 145 of the DGCL empowers any corporation to indemnify its directors
  and officers and to purchase insurance with respect to liability arising out of
  their capacity or status as directors and officers, provided that this provision
  shall not eliminate or limit the liability of a director: (i) for any breach of
  the director's duty of loyalty to the corporation or its stockholders, (ii) for
  acts or omissions not in good faith or which involve intentional misconduct or a
  knowing violation of law, (iii) arising under Section 174 of the DGCL, or (iv)
  for any transaction from which the director derived an improper personal
  benefit. The DGCL provides further that the indemnification permitted thereunder
  shall not be deemed exclusive of any other rights to which the directors and
  officers may be entitled under the corporation's bylaws, any agreement, a vote
  of stockholders or otherwise. The Charter eliminates the personal liability of
  directors to the fullest extent permitted by Section 102(b)(7) of the DGCL and
  provides that the Registrant shall fully indemnify any person who was or is a
  party or is threatened to be made a party to any threatened, pending or
  completed action, suit or proceeding (whether civil, criminal, administrative or
  investigative) by reason of the fact that such person is or was a director or
  officer of the Registrant, or is or was serving at the request of the Registrant
  as a director or officer of another corporation, partnership, joint venture,
  trust, employee benefit plan or other enterprise, against expenses (including
  attorney's fees), judgments, fines and amounts paid in settlement actually and
  reasonably incurred by such person in connection with such action, suit or
  proceeding.
  
       At present, there is no pending litigation or proceeding involving any
  director, officer, employee or agent as to which indemnification will be
  required or permitted under the Charter. The Registrant is not aware of any
  threatened litigation or proceeding that may result in a claim for such
  indemnification.
  
  
  
  
                                        -3-
  <PAGE>   4
  
       Article EIGHTH of the Registrant's Charter provides that no director of the
  registrant shall be personally liable for any monetary damages for any breach of
  fiduciary duty as a director, except to the extent that the Delaware General
  Corporation Law statute prohibits the elimination or limitation of liability of
  directors for breach of fiduciary duty.
  
       Article NINTH of the Registrant's Charter provides that a director or
  officer of the registrant (a) shall be indemnified by the registrant against all
  expenses (including attorneys' fees), judgments, 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 interests of the registrant, and, with respect to any criminal
  action or proceeding, had no reasonable cause to believe his conduct was
  unlawful and (b) shall be indemnified by the registrant against all expenses
  (including attorneys' fees) 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 registrant, 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 unless the registrant determines
  that the applicable standard of conduct required for indemnification has not
  been met. In the event of a determination by the registrant that the director or
  officer did not meet the applicable standard of conduct required for
  indemnification, or if the registrant fails to make an indemnification payment
  within 60 days after such payment is claimed by such person, 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 Charter further provides that the
  indemnification provided therein is not exclusive, and provides that in the
  event that the Delaware General Corporation Law statute is amended to expand the
  indemnification permitted to directors or officers the registrant must indemnify
  those persons to the full extent permitted by such law as so amended.
  
       ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.
  
       Not applicable.
  
       ITEM 8. EXHIBITS.
  
       The Exhibit Index immediately preceding the exhibits is incorporated herein
  by reference.
  
  
  
  
  
                                        -4-
  <PAGE>   5
  
       ITEM 9. UNDERTAKINGS.
  
       1. 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. 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) if, in the aggregate, the changes in volume and
       price represent no more than 20 percent change in the maximum aggregate
       offering price set forth in the "Calculation of Registration Fee" table in
       the effective 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 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 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.
  
       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 Securities and Exchange Commission
  such indemnification is against public policy as expressed in the
  
  
                                        -5-
  
  <PAGE>   6
  
  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.
  
                      [Rest of Page Intentionally Left Blank.]
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
                                        -6-
  
  <PAGE>   7
  
  
                                     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 Cambridge, Massachusetts, on this 30th day of August, 2000.
  
                                          THE MEDICINES COMPANY
  
                                          By: /s/ Peyton J. Marshall
                                             ----------------------------
                                             Peyton J. Marshall
                                             Chief Financial Officer
  
                          POWER OF ATTORNEY AND SIGNATURES
  
       We, the undersigned officers and directors of The Medicines Company, Inc.,
  hereby severally constitute and appoint Clive A. Meanwell and Peyton J.
  Marshall, 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 The Medicines Company, 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 below by the following persons in the
  capacities and on the dates indicated.
  
        SIGNATURE                    TITLE                              DATE
  
  
  /s/ Clive A. Meanwell     President, Chief Executive             August 30, 2000
  -----------------------   Officer and Director (Principal
  Clive A. Meanwell         Executive Officer)
  
  
  /s/ Peyton J. Marshall    Chief Financial Officer                August 30, 2000
  -----------------------   (Principal Financial and
  Peyton J. Marshall        Accounting Officer)
  
  
                            Director                               August __, 2000
  -----------------------
  Dennis B. Gillings
  
                            Director                               August __, 2000
  -----------------------
  Anders D. Hove
  
  
  
                                        -7-
  <PAGE>   8
  
  ------------------------  Director                               August __, 2000
  M. Fazle Husain
  
  
  /s/ T. Scott Johnson      Director                               August 30, 2000
  ------------------------
  T. Scott Johnson
  
  
  /s/ Armin M. Kessler      Director                               August 30, 2000
  ------------------------
  Armin M. Kessler
  
  
  /s/ James E. Thomas       Director                               August 30, 2000
  ------------------------
  James E. Thomas
  
  
  /s/ Robert Yedid          Director                               August __, 2000
  ------------------------
  Robert Yedid
  
  
                            Director                               August __, 2000
  ------------------------
  Leonard Bell
  
  
  
  
  
                                        -8-
  
  
  <PAGE>   9
  
  
  
                                  INDEX TO EXHIBITS
  
  NUMBER    DESCRIPTION
  3.1(1)    Third Amended and Restated Certificate of Incorporation of the
            Registrant
  
  3.2(1)    Amended and Restated By-Laws of the Registrant
  
  4.1(1)    Specimen stock certificate of common stock of the Registrant
  
  5.1       Opinion of Hale and Dorr LLP, counsel to the Registrant
  
  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 in the signature pages of this
            registration statement)
  
  ------------
  
  (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. 333-37404) and incorporated herein by reference.
  
  
  
  
  
  
                                        -9-
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metadata_filer: {"company-data": {"conformed-name": "MEDICINES CO/ MA", "cik": "0001113481", "assigned-sic": "2834", "irs-number": "043324394", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-44884", "film-number": "714490"}, "business-address": {"street1": "ONE CAMBRIDGE CTR", "city": "CAMBRIDGE", "state": "MA", "zip": "02142", "phone": "6172259099"}}
text: 1
       As filed with the Securities and Exchange Commission on August 31, 2000
                                                         Registration No. 333-____
  ================================================================================
  
                         SECURITIES AND EXCHANGE COMMISSION
                               WASHINGTON, D.C. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                                THE MEDICINES COMPANY
               (Exact Name of Registrant as Specified in Its Charter)
  
           DELAWARE                                        04-3324394
  (State or Other Jurisdiction of                       (I.R.S. Employer
  Incorporation or Organization)                       Identification No.)
  
  ONE CAMBRIDGE CENTER, CAMBRIDGE, MASSACHUSETTS             02142
  (Address of Principal Executive Offices)                 (Zip Code)
  
                              1998 STOCK INCENTIVE PLAN
                       2000 OUTSIDE DIRECTOR STOCK OPTION PLAN
                          2000 EMPLOYEE STOCK PURCHASE PLAN
                              (Full Title of the Plan)
  
                                  CLIVE A. MEANWELL
                               CHIEF EXECUTIVE OFFICER
                                THE MEDICINES COMPANY
                                ONE CAMBRIDGE CENTER
                           CAMBRIDGE, MASSACHUSETTS 02142
                       (Name and Address of Agent for Service)
                                   (617) 225-9099
            (Telephone number, Including Area Code, of Agent For Service)
  
                           CALCULATION OF REGISTRATION FEE
  ================================================================================================================
  Title of Each Class                               Proposed Maximum       Proposed Maximum
  of Securities to                                 Offering Price Per     Aggregate Offering          Amount of
  be  Registered        Amount to be Registered           Share                  Price            Registration Fee
  ----------------------------------------------------------------------------------------------------------------
  Common Stock,
  $0.001 par value          4,873,759 shares           $18.938(1)           $92,299,248(1)           $24,367(1)
  per share
  ================================================================================================================
  (1)  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
       August 30, 2000.
  2
  
  PART I. INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS
  
       ITEM 1. PLAN INFORMATION.
  
       The information required by Part I is included in documents sent or given
  to participants in the 1998 Stock Incentive Plan, the 2000 Outside Director
  Stock Option Plan and the 2000 Employee Stock Purchase Plan of The Medicines
  Company 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 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 Common Stock of the registrant, $0.01 par value
  per share (the "Common Stock"), contained in the registrant's registration
  statement on Form 8-A and 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 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.
  
                                        -2-
  3
  
       ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.
  
       Hale and Dorr LLP has opined as to the legality of the securities being
  offered by this registration statement. Partners of Hale and Dorr LLP
  beneficially own an aggregate of 23,634 shares of Common Stock and a warrant to
  purchase an aggregate of 1,554 shares of Common Stock.
  
       ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.
  
       The Registrant's Third Amended and Restated Certificate of Incorporation,
  as amended to date (the "Charter") provides that, except to the extent
  prohibited by the Delaware General Corporation Law (the "DGCL"), the
  Registrant's directors shall not be personally liable to the Registrant or its
  stockholders for monetary damages for any breach of fiduciary duty as directors
  of the Registrant. Under the DGCL, the directors have a fiduciary duty to the
  Registrant which is not eliminated by this provision of the Charter and, in
  appropriate circumstances, equitable remedies such as injunctive or other forms
  of nonmonetary relief will remain available. In addition, each director will
  continue to be subject to liability under the DGCL for breach of the director's
  duty of loyalty to the Registrant, for acts or omissions which are found by a
  court of competent jurisdiction to be not in good faith or involving intentional
  misconduct, for knowing violations of law, for actions leading to improper
  personal benefit to the director, and for payment of dividends or approval of
  stock repurchases or redemptions that are prohibited by DGCL. This provision
  also does not affect the directors' responsibilities under any other laws, such
  as the Federal securities laws or state or Federal environmental laws. The
  Registrant has obtained liability insurance for its officers and directors.
  
       Section 145 of the DGCL empowers any corporation to indemnify its directors
  and officers and to purchase insurance with respect to liability arising out of
  their capacity or status as directors and officers, provided that this provision
  shall not eliminate or limit the liability of a director: (i) for any breach of
  the director's duty of loyalty to the corporation or its stockholders, (ii) for
  acts or omissions not in good faith or which involve intentional misconduct or a
  knowing violation of law, (iii) arising under Section 174 of the DGCL, or (iv)
  for any transaction from which the director derived an improper personal
  benefit. The DGCL provides further that the indemnification permitted thereunder
  shall not be deemed exclusive of any other rights to which the directors and
  officers may be entitled under the corporation's bylaws, any agreement, a vote
  of stockholders or otherwise. The Charter eliminates the personal liability of
  directors to the fullest extent permitted by Section 102(b)(7) of the DGCL and
  provides that the Registrant shall fully indemnify any person who was or is a
  party or is threatened to be made a party to any threatened, pending or
  completed action, suit or proceeding (whether civil, criminal, administrative or
  investigative) by reason of the fact that such person is or was a director or
  officer of the Registrant, or is or was serving at the request of the Registrant
  as a director or officer of another corporation, partnership, joint venture,
  trust, employee benefit plan or other enterprise, against expenses (including
  attorney's fees), judgments, fines and amounts paid in settlement actually and
  reasonably incurred by such person in connection with such action, suit or
  proceeding.
  
       At present, there is no pending litigation or proceeding involving any
  director, officer, employee or agent as to which indemnification will be
  required or permitted under the Charter. The Registrant is not aware of any
  threatened litigation or proceeding that may result in a claim for such
  indemnification.
  
                                        -3-
  4
  
       Article EIGHTH of the Registrant's Charter provides that no director of the
  registrant shall be personally liable for any monetary damages for any breach of
  fiduciary duty as a director, except to the extent that the Delaware General
  Corporation Law statute prohibits the elimination or limitation of liability of
  directors for breach of fiduciary duty.
  
       Article NINTH of the Registrant's Charter provides that a director or
  officer of the registrant (a) shall be indemnified by the registrant against all
  expenses (including attorneys' fees), judgments, 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 interests of the registrant, and, with respect to any criminal
  action or proceeding, had no reasonable cause to believe his conduct was
  unlawful and (b) shall be indemnified by the registrant against all expenses
  (including attorneys' fees) 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 registrant, 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 unless the registrant determines
  that the applicable standard of conduct required for indemnification has not
  been met. In the event of a determination by the registrant that the director or
  officer did not meet the applicable standard of conduct required for
  indemnification, or if the registrant fails to make an indemnification payment
  within 60 days after such payment is claimed by such person, 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 Charter further provides that the
  indemnification provided therein is not exclusive, and provides that in the
  event that the Delaware General Corporation Law statute is amended to expand the
  indemnification permitted to directors or officers the registrant must indemnify
  those persons to the full extent permitted by such law as so amended.
  
       ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.
  
       Not applicable.
  
       ITEM 8. EXHIBITS.
  
       The Exhibit Index immediately preceding the exhibits is incorporated herein
  by reference.
  
                                        -4-
  5
  
       ITEM 9. UNDERTAKINGS.
  
       1. 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. 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) if, in the aggregate, the changes in volume and
       price represent no more than 20 percent change in the maximum aggregate
       offering price set forth in the "Calculation of Registration Fee" table in
       the effective 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 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 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.
  
       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 Securities and Exchange Commission
  such indemnification is against public policy as expressed in the
  
                                        -5-
  6
  
  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.
  
                      [Rest of Page Intentionally Left Blank.]
  
                                        -6-
  7
  
                                     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 Cambridge, Massachusetts, on this 30th day of August, 2000.
  
                                          THE MEDICINES COMPANY
  
                                          By: /s/ Peyton J. Marshall
                                             ----------------------------
                                             Peyton J. Marshall
                                             Chief Financial Officer
  
                          POWER OF ATTORNEY AND SIGNATURES
  
       We, the undersigned officers and directors of The Medicines Company, Inc.,
  hereby severally constitute and appoint Clive A. Meanwell and Peyton J.
  Marshall, 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 The Medicines Company, 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 below by the following persons in the
  capacities and on the dates indicated.
  
        SIGNATURE                    TITLE                              DATE
  
  /s/ Clive A. Meanwell     President, Chief Executive             August 30, 2000
  -----------------------   Officer and Director (Principal
  Clive A. Meanwell         Executive Officer)
  
  /s/ Peyton J. Marshall    Chief Financial Officer                August 30, 2000
  -----------------------   (Principal Financial and
  Peyton J. Marshall        Accounting Officer)
  
                            Director                               August __, 2000
  -----------------------
  Dennis B. Gillings
  
                            Director                               August __, 2000
  -----------------------
  Anders D. Hove
  
                                        -7-
  8
  
  ------------------------  Director                               August __, 2000
  M. Fazle Husain
  
  /s/ T. Scott Johnson      Director                               August 30, 2000
  ------------------------
  T. Scott Johnson
  
  /s/ Armin M. Kessler      Director                               August 30, 2000
  ------------------------
  Armin M. Kessler
  
  /s/ James E. Thomas       Director                               August 30, 2000
  ------------------------
  James E. Thomas
  
  /s/ Robert Yedid          Director                               August __, 2000
  ------------------------
  Robert Yedid
  
                            Director                               August __, 2000
  ------------------------
  Leonard Bell
  
                                        -8-
  9
  
                                  INDEX TO EXHIBITS
  
  NUMBER    DESCRIPTION
  3.1(1)    Third Amended and Restated Certificate of Incorporation of the
            Registrant
  
  3.2(1)    Amended and Restated By-Laws of the Registrant
  
  4.1(1)    Specimen stock certificate of common stock of the Registrant
  
  5.1       Opinion of Hale and Dorr LLP, counsel to the Registrant
  
  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 in the signature pages of this
            registration statement)
  
  ------------
  
  (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. 333-37404) and incorporated herein by reference.
  
                                        -9-