content: <PAGE>   1
  
  
        As filed with the Securities and Exchange Commission on May 16, 2000
  
                                                     Registration No. 333-
  
  ================================================================================
  
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D.C. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                            ASPECT MEDICAL SYSTEMS, INC.
               (Exact Name of Registrant as Specified in Its Charter)
  
           DELAWARE                                          04-2985553
  (State or Other Jurisdiction of                         (I.R.S. Employer
   Incorporation or Organization)                        Identification No.)
  
  141 NEEDHAM STREET, NEWTON, MASSACHUSETTS                   02464
  (Address of Principal Executive Offices)                 (Zip Code)
  
                     AMENDED AND RESTATED 1991 STOCK OPTION PLAN
                              1998 STOCK INCENTIVE PLAN
                           1998 DIRECTOR STOCK OPTION PLAN
                     RESTATED 1999 EMPLOYEE STOCK PURCHASE PLAN
                              (Full Title of the Plan)
  
                                  NASSIB G. CHAMOUN
                        PRESIDENT AND CHIEF EXECUTIVE OFFICER
                            ASPECT MEDICAL SYSTEMS, INC.
                                 141 NEEDHAM STREET
                             NEWTON, MASSACHUSETTS 02464
                       (Name and Address of Agent for Service)
                                   (617) 559-7000
            (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         Amount to be            Offering Price      Aggregate Offering          Amount of
    be  Registered            Registered               Per Share                Price            Registration Fee
  ------------------------------------------------------------------------------------------------------------------
  <S>                       <C>                     <C>                    <C>                     <C>
  Common Stock, $0.01
  par value per share       6,860,000 shares           $45.7815(1)         $314,061,090(1)          $82,913(1)
  ==================================================================================================================
  </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 May
       15, 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 Amended and Restated 1991 Stock Option Plan, the 1998
  Stock Incentive Plan, the 1998 Director Stock Option Plan and the Restated 1999
  Employee Stock Purchase Plan of Aspect Medical Systems, Inc. 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 prospectus 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.
  
       ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
  
       Article EIGHTH of the registrant's Restated Certificate of Incorporation
  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 Restated Certificate of Incorporation
  provides that a director or officer of the registrant (a) shall be indemnified
  by the registrant against all expenses (including attorneys' fees), 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 Restated Certificate of Incorporation
  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.
  
                                        -3-
  
  <PAGE>   4
  
       Section 145 of the Delaware General Corporation Law statute provides that a
  corporation has the power to indemnify a director, officer, employee or agent of
  the corporation and certain other persons serving at the request of the
  corporation in related capacities against amounts paid and expenses incurred in
  connection with an action or proceeding to which he is or is threatened to be
  made a party by reason of such position, if such person shall have acted in good
  faith and in a manner he reasonably believed to be in or not opposed to the best
  interests of the corporation, and, in any criminal proceeding, if such person
  had no reasonable cause to believe his conduct was unlawful; provided that, in
  the case of actions brought by or in the right of the corporation, no
  indemnification shall be made with respect to any matter as to which such person
  shall have been adjudged to be liable to the corporation unless and only to the
  extent that the adjudicating court determines that such indemnification is
  proper under the circumstances.
  
       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.
  
       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; 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.
  
                                        -4-
  
  <PAGE>   5
  
           (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 (and, where applicable, each filing of an employee benefit plan's
  annual report pursuant to 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 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.
  
  
                                        -5-
  
  <PAGE>   6
                                     SIGNATURES
  
       Pursuant to the requirements of the Securities Act, the Registrant
  certifies that it has reasonable grounds to believe that it meets all of the
  requirements for filing on Form S-8 and has duly caused this Registration
  Statement to be signed on its behalf by the undersigned, thereunto duly
  authorized, in Newton, Massachusetts, on this 9th day of May, 2000.
  
                                        ASPECT MEDICAL SYSTEMS, INC.
  
                                        By: /s/ J. Neal Armstrong
                                           -----------------------------------
                                            J. Neal Armstrong
                                            Vice President and Chief Financial
                                            Officer
  
                          POWER OF ATTORNEY AND SIGNATURES
  
       We, the undersigned officers and directors of Aspect Medical Systems, Inc.,
  hereby severally constitute and appoint Nassib G. Chamoun, J. Breckenridge Eagle
  and J. Neal Armstrong, 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 Aspect Medical Systems, 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 below by the following persons in the
  capacities and on the dates indicated.
  
  <TABLE>
  <CAPTION>
               SIGNATURE                              TITLE                               DATE
               ---------                              -----                               ----
  <S>                                   <C>                                            <C>
  /s/ Nassib G. Chamoun                 President, Chief Executive                     May 9, 2000
  -----------------------------         Officer and Director (Principal
  Nassib G. Chamoun                     Executive Officer)
  
  
  
  /s/ J. Breckenridge Eagle             Chairman of the Board of                       May 9, 2000
  -----------------------------         Directors
  J. Breckenridge Eagle
  
  
  /s/ J. Neal Armstrong                 Vice President and Chief                       May 9, 2000
  -----------------------------         Financial Officer (Principal
  J. Neal Armstrong                     Financial and Accounting Officer)
  
  
  
  /s/ Boudewijn L.P.M. Bollen           Director                                       May 9, 2000
  -----------------------------
  Boudewijn L.P.M. Bollen
  
  </TABLE>
  
                                        -6-
  <PAGE>   7
  
  <TABLE>
  <CAPTION>
               SIGNATURE                              TITLE                               DATE
               ---------                              -----                               ----
  <S>                                   <C>                                            <C>
  /s/ Stephen E. Coit                   Director                                       May 9, 2000
  -----------------------------
  Stephen E. Coit
  
  
  /s/ Edwin M. Kania                    Director                                       May 9, 2000
  -----------------------------
  Edwin M. Kania
  
  
  /s/ Lester J. Lloyd                   Director                                       May 9, 2000
  ------------------------------
  Lester J. Lloyd
  
  
  /s/ Terrance McGuire                  Director                                       May 9, 2000
  ------------------------------
  Terrance McGuire
  
  
  /s/ Donald Stanski                    Director                                       May 9, 2000
  ------------------------------
  Donald Stanski
  </TABLE>
  
                                        -7-
  
  
  <PAGE>   8
  
  
  
                                  INDEX TO EXHIBITS
  
  NUMBER             DESCRIPTION
  ------             -----------
  
   3.1(1)            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 Arthur Andersen 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. 333-86295) and incorporated herein by reference.
  
  
  
                                        -8-
metadata_documents: [{"type": "S-8", "sequence": "1", "description": "ASPECT MEDICAL SYSTEMS, INC.", "secsgml_size_bytes": 20113}]
metadata_filer: {"company-data": {"conformed-name": "ASPECT MEDICAL SYSTEMS INC", "cik": "0000886235", "assigned-sic": "3845", "irs-number": "042985553", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-37130", "film-number": "637472"}, "business-address": {"street1": "TWO VISION DRIVE", "city": "NATICK", "state": "MA", "zip": "01760", "phone": "5086530603"}, "mail-address": {"street1": "TWO VISION DRIVE", "city": "NATICK", "state": "MA", "zip": "01760"}}
text: 1
  
        As filed with the Securities and Exchange Commission on May 16, 2000
  
                                                     Registration No. 333-
  
  ================================================================================
  
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D.C. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                            ASPECT MEDICAL SYSTEMS, INC.
               (Exact Name of Registrant as Specified in Its Charter)
  
           DELAWARE                                          04-2985553
  (State or Other Jurisdiction of                         (I.R.S. Employer
   Incorporation or Organization)                        Identification No.)
  
  141 NEEDHAM STREET, NEWTON, MASSACHUSETTS                   02464
  (Address of Principal Executive Offices)                 (Zip Code)
  
                     AMENDED AND RESTATED 1991 STOCK OPTION PLAN
                              1998 STOCK INCENTIVE PLAN
                           1998 DIRECTOR STOCK OPTION PLAN
                     RESTATED 1999 EMPLOYEE STOCK PURCHASE PLAN
                              (Full Title of the Plan)
  
                                  NASSIB G. CHAMOUN
                        PRESIDENT AND CHIEF EXECUTIVE OFFICER
                            ASPECT MEDICAL SYSTEMS, INC.
                                 141 NEEDHAM STREET
                             NEWTON, MASSACHUSETTS 02464
                       (Name and Address of Agent for Service)
                                   (617) 559-7000
            (Telephone number, Including Area Code, of Agent For Service)
  
                           CALCULATION OF REGISTRATION FEE
  ==================================================================================================================
  Title of Each Class                               Proposed Maximum       Proposed Maximum
    of Securities to         Amount to be            Offering Price      Aggregate Offering          Amount of
    be  Registered            Registered               Per Share                Price            Registration Fee
  ------------------------------------------------------------------------------------------------------------------
  Common Stock, $0.01
  par value per share       6,860,000 shares           $45.7815(1)         $314,061,090(1)          $82,913(1)
  ==================================================================================================================
  (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 May
       15, 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 Amended and Restated 1991 Stock Option Plan, the 1998
  Stock Incentive Plan, the 1998 Director Stock Option Plan and the Restated 1999
  Employee Stock Purchase Plan of Aspect Medical Systems, Inc. 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 prospectus 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.
  
       ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
  
       Article EIGHTH of the registrant's Restated Certificate of Incorporation
  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 Restated Certificate of Incorporation
  provides that a director or officer of the registrant (a) shall be indemnified
  by the registrant against all expenses (including attorneys' fees), 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 Restated Certificate of Incorporation
  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.
  
                                        -3-
  4
  
       Section 145 of the Delaware General Corporation Law statute provides that a
  corporation has the power to indemnify a director, officer, employee or agent of
  the corporation and certain other persons serving at the request of the
  corporation in related capacities against amounts paid and expenses incurred in
  connection with an action or proceeding to which he is or is threatened to be
  made a party by reason of such position, if such person shall have acted in good
  faith and in a manner he reasonably believed to be in or not opposed to the best
  interests of the corporation, and, in any criminal proceeding, if such person
  had no reasonable cause to believe his conduct was unlawful; provided that, in
  the case of actions brought by or in the right of the corporation, no
  indemnification shall be made with respect to any matter as to which such person
  shall have been adjudged to be liable to the corporation unless and only to the
  extent that the adjudicating court determines that such indemnification is
  proper under the circumstances.
  
       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.
  
       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; 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.
  
                                        -4-
  5
  
           (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 (and, where applicable, each filing of an employee benefit plan's
  annual report pursuant to 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 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.
  
                                        -5-
  6
                                     SIGNATURES
  
       Pursuant to the requirements of the Securities Act, the Registrant
  certifies that it has reasonable grounds to believe that it meets all of the
  requirements for filing on Form S-8 and has duly caused this Registration
  Statement to be signed on its behalf by the undersigned, thereunto duly
  authorized, in Newton, Massachusetts, on this 9th day of May, 2000.
  
                                        ASPECT MEDICAL SYSTEMS, INC.
  
                                        By: /s/ J. Neal Armstrong
                                           -----------------------------------
                                            J. Neal Armstrong
                                            Vice President and Chief Financial
                                            Officer
  
                          POWER OF ATTORNEY AND SIGNATURES
  
       We, the undersigned officers and directors of Aspect Medical Systems, Inc.,
  hereby severally constitute and appoint Nassib G. Chamoun, J. Breckenridge Eagle
  and J. Neal Armstrong, 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 Aspect Medical Systems, 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 below by the following persons in the
  capacities and on the dates indicated.
  SIGNATURE                              TITLE                               DATE
               ---------                              -----                               ----
  /s/ Nassib G. Chamoun                 President, Chief Executive                     May 9, 2000
  -----------------------------         Officer and Director (Principal
  Nassib G. Chamoun                     Executive Officer)
  
  /s/ J. Breckenridge Eagle             Chairman of the Board of                       May 9, 2000
  -----------------------------         Directors
  J. Breckenridge Eagle
  
  /s/ J. Neal Armstrong                 Vice President and Chief                       May 9, 2000
  -----------------------------         Financial Officer (Principal
  J. Neal Armstrong                     Financial and Accounting Officer)
  
  /s/ Boudewijn L.P.M. Bollen           Director                                       May 9, 2000
  -----------------------------
  Boudewijn L.P.M. Bollen
  -6-
  7
  SIGNATURE                              TITLE                               DATE
               ---------                              -----                               ----
  /s/ Stephen E. Coit                   Director                                       May 9, 2000
  -----------------------------
  Stephen E. Coit
  
  /s/ Edwin M. Kania                    Director                                       May 9, 2000
  -----------------------------
  Edwin M. Kania
  
  /s/ Lester J. Lloyd                   Director                                       May 9, 2000
  ------------------------------
  Lester J. Lloyd
  
  /s/ Terrance McGuire                  Director                                       May 9, 2000
  ------------------------------
  Terrance McGuire
  
  /s/ Donald Stanski                    Director                                       May 9, 2000
  ------------------------------
  Donald Stanski
  -7-
  8
  
                                  INDEX TO EXHIBITS
  
  NUMBER             DESCRIPTION
  ------             -----------
  
   3.1(1)            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 Arthur Andersen 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. 333-86295) and incorporated herein by reference.
  
                                        -8-