content: <PAGE>   1
             As filed with the Securities and Exchange Commission on July 28, 2000
  
                                                        Registration No. 333-_____
  
  
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D.C. 20549
  
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
  
                               ASPEN TECHNOLOGY, INC.
               (Exact Name of Registrant as Specified in Its Charter)
  
                                      Delaware
           (State or Other Jurisdiction of Incorporation or Organization)
  
                                     04-2739697
                        (I.R.S. Employer Identification No.)
  
                 Ten Canal Park, Cambridge, Massachusetts   02141
                 (Address of Principal Executive Offices) (Zip Code)
  
  
                      Petrolsoft Corporation Stock Option Plan
                              (Full Title of the Plan)
  
  
                                  Lawrence B. Evans
                  Chairman of the Board and Chief Executive Officer
                               Aspen Technology, Inc.
                                   Ten Canal Park
                           Cambridge, Massachusetts 02141
                       (Name and Address of Agent for Service)
  
                                   (617) 949-1000
            (Telephone Number, Including Area Code, of Agent For Service)
  
  
  
  
                           CALCULATION OF REGISTRATION FEE
  
  <TABLE>
  <CAPTION>
  ------------------------------------------------------------------------------------------------------------------
                                                                   Proposed         Proposed
                                                                    Maximum          Maximum
              Title of Securities                  Amount       Offering Price  Aggregate Offering     Amount of
               To Be Registered               To Be Registered     Per Share          Price        Registration Fee
  ------------------------------------------------------------------------------------------------------------------
  <S>                                         <C>               <C>             <C>                <C>
  Common Stock, $.10 par value..............       123,885         $11.36(1)     $1,407,333.60(1)      $371.54
  ------------------------------------------------------------------------------------------------------------------
  </TABLE>
  
  (1)  Calculated in accordance with Rule 457(h) under the Securities Act of 1933.
  
  
  <PAGE>   2
  
  
  
  PART I. INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS
  
          The information required by Part I is included in documents sent or
  given to participants in the Petrolsoft Corporation Stock Option Plan pursuant
  to Rule 428(b)(1) of the Securities Act of 1933, as amended (the "Securities
  Act").
  
  PART II. INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
  
  Item 3. INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE
  
          The Registrant is subject to the informational and reporting
  requirements of Sections 13(a), 13(c), 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 filed with the
  Commission, are incorporated in this Registration Statement by reference:
  
          (1)  The Registrant's latest prospectus filed pursuant to Rule 424(b)
               under the Securities Act that contains audited financial statements
               for the Registrant's latest fiscal year for which such statements
               have been filed.
  
          (2)  All other reports filed pursuant to Section 13(a) or 15(d) of the
               Exchange Act since the end of the fiscal year covered by the
               prospectus referred to in (1) above.
  
          (3)  The description of the common stock of the Registrant, $.10 par
               value per share (the "Common Stock"), contained in the Registrant's
               registration statement on Form 8-A filed with the Commission under
               Section 12(g) of 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.
  
  
                                        -2-
  <PAGE>   3
  
  Item 4. DESCRIPTION OF SECURITIES
  
          Not applicable.
  
  Item 5. INTERESTS OF NAMED EXPERTS AND COUNSEL
  
          Not applicable.
  
  Item 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS
  
          Article SEVENTH of the Registrant's Certificate of Incorporation, as
  amended (the "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 prohibits the elimination or limitation of liability of
  directors for breach of fiduciary duty.
  
          Article EIGHTH of the Certificate of Incorporation provides that a
  director or officer of the Registrant shall be indemnified by the Registrant
  against:
  
          (a)  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 or her by virtue
               of his or her position as a director or officer of the Registrant
               if he or she acted 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 or her conduct was unlawful
               and
  
          (b)  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 or her by virtue of his
               or her position as a director or officer of the Registrant if he or
               she 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
               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 or she 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 the dismissal of an
  action without prejudice, he or she 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
  or her request, provided that he or she undertakes to repay the amount advanced
  if it is ultimately determined that he or she 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 sixty 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 EIGHTH of the 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 is amended to expand the
  indemnification permitted to directors or officers the Registrant must indemnify
  those persons to the fullest extent permitted by such law as so amended.
  
          Section 145 of the Delaware General Corporation Law 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
  
  
                                        -3-
  <PAGE>   4
  
  
  
  proceeding to which he or she 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 or she 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 or her 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.
  
          The Registrant maintains a directors' and officers' insurance policy
  that covers certain liabilities of directors and officers of the Registrant,
  including liabilities under the Securities Act of 1933. The Registrant maintains
  a general liability insurance policy that covers certain liabilities of
  directors and officers of the Registrant arising out of claims based on acts or
  omissions in their capacities as directors or officers.
  
  Item 7. EXEMPTION FROM REGISTRATION CLAIMED
  
          Not applicable.
  
  Item 8. EXHIBITS
  
          The following exhibits are filed as part of this Registration Statement:
  
          4.1  Certificate of Incorporation of the Registrant. Incorporated by
               reference to an exhibit to the Registrant's Form 8-K dated March
               12, 1998 (filed March 27, 1998).
  
          4.2  By-Laws of the Registrant. Incorporated by reference to an exhibit
               to the Registrant's Registration Statement on Form 8-A (filed on
               September 13, 1994), as amended by Amendment No. 1 thereto (filed
               on June 12, 1998).
  
          4.3  Rights Agreement dated as of October 9, 1997, between the
               Registrant and American Stock Transfer and Trust Company, as Rights
               Agent. Incorporated by reference to an exhibit to the Registrant's
               Registration Statement on Form 8-A (filed on October 10, 1997), as
               amended by Amendment No. 1 thereto (filed on June 12, 1998).
  
          4.4  Specimen certificate representing Rights to Purchase Series A
               Participating Cumulative Preferred Stock of Aspen Technology, Inc.
               Incorporated by reference to Exhibit B to the Rights Agreement
               referenced in Exhibit 4.3.
  
          4.5  Specimen certificate for the Registrant's common stock, $.10 par
               value. Incorporated by reference to an exhibit to the Registrant's
               Registration Statement on Form 8-A (filed on October 10, 1997), as
               amended by Amendment No. 1 thereto (filed on June 12, 1998) and
               incorporated herein by reference.
  
          4.6  Registrant's Petrolsoft Corporation Stock Option Plan.
  
          5.1  Opinion of Hale and Dorr LLP.
  
         23.1  Consent of Arthur Andersen LLP.
  
         23.2  Consent of Hale and Dorr LLP (included in Exhibit 5.1).
  
         24.1  Power of Attorney (included in the signature page of this
               Registration Statement).
  
  
  Item 9. UNDERTAKINGS
  
          The Registrant hereby undertakes:
  
          (1)  to file, during any period in which offers or sales are being made,
               a post-effective amendment to this Registration Statement to
               include any material information with respect to the plan of
               distribution not
  
  
                                        -4-
  <PAGE>   5
  
  
  
               previously disclosed in the Registration Statement or any material
               change to such information 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; and
  
          (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 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 in 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 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 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, Massachusetts, on this twenty-fourth day
  of July, 2000.
  
                                            ASPEN TECHNOLOGY, INC.
  
  
                                            By: /s/ Lawrence B. Evans
                                                ----------------------------------
                                                Lawrence B. Evans
                                                Chief Executive Officer
  
  
                                        -6-
  <PAGE>   7
  
  
                                  POWER OF ATTORNEY
  
       We, the undersigned officers and directors of Aspen Technology, Inc.
  hereby severally constitute and appoint Lawrence B. Evans and Lisa W. Zappala,
  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 behalf in our capacities as officers and
  directors to enable Aspen Technology, Inc. to comply with all requirements
  of the Securities and Exchange Commission, hereby ratifying and confirming our
  signatures as they may be signed by 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 indicated, as of July 21, 2000.
  
  <TABLE>
  <CAPTION>
           NAME                                           TITLE
           ----                                           -----
  <S>                                                     <C>
  /s/ Lawrence B. Evans
  ___________________________________________________     Chairman of the Board and Chief Executive Officer
  Lawrence B. Evans                                       (principal executive officer)
  
  
  /s/ Lisa W. Zappala
  ___________________________________________________     Senior Vice President and Chief Financial Officer
  Lisa W. Zappala                                         (principal financial and accounting officer)
  
  
  /s/ Joseph F. Boston
  ___________________________________________________     Director
  Joseph F. Boston
  
  
  ___________________________________________________     Director
  Gresham T. Brebach, Jr.
  
  
  ___________________________________________________     Director
  Douglas R. Brown
  
  
  /s/ Stephen L. Brown
  ___________________________________________________     Director
  Stephen L. Brown
  
  
  /s/ /Stephen M. Jennings
  ___________________________________________________     Director
  Stephen M. Jennings
  
  
  /s/ Joan C. McArdle
  ___________________________________________________     Director
  Joan C. McArdle
  
  
  ___________________________________________________     Director
  Alison Ross
  
  </TABLE>
  
  
                                        -7-
  <PAGE>   8
  
  
  
                                    EXHIBIT INDEX
  
  <TABLE>
  <CAPTION>
  Exhibit
  Number                 Description
  -------                -----------
  
  <S>           <C>
    4.1         Certificate of Incorporation of the Registrant. Incorporated by reference to an exhibit to the
                Registrant's Form 8-K dated March 12, 1998 (filed March 27, 1998).
  
    4.2         By-Laws of the Registrant. Incorporated by reference to an exhibit to the Registrant's Registration
                Statement on Form 8-A (filed on September 13, 1994), as amended by Amendment No. 1 thereto (filed
                on June 12, 1998).
  
    4.3         Rights Agreement dated as of October 9, 1997, between the Registrant and American Stock Transfer
                and Trust Company, as Rights Agent. Incorporated by reference to an exhibit to the Registrant's
                Registration Statement on Form 8-A (filed on October 10, 1997), as amended by Amendment No. 1
                thereto (filed on June 12, 1998).
  
    4.4         Specimen certificate representing Rights to Purchase Series A Participating Cumulative Preferred
                Stock of Aspen Technology, Inc. Incorporated by reference to Exhibit B to the Rights Agreement
                referenced in Exhibit 4.3.
  
    4.5         Specimen certificate for the Registrant's common stock, $.10 par value. Incorporated by reference to
                an exhibit to the Registrant's Registration Statement on Form 8-A (filed on October 10, 1997), as
                amended by Amendment No. 1 thereto (filed on June 12, 1998) and incorporated herein by reference.
  
    4.6         Registrant's Petrolsoft Corporation Stock Option Plan.
  
    5.1         Opinion of Hale and Dorr LLP.
  
   23.1         Consent of Arthur Andersen LLP.
  
   23.2         Consent of Hale and Dorr LLP (included in Exhibit 5.1).
  
   24.1         Power of Attorney (included in the signature page of this Registration Statement).
  </TABLE>
  
  
                                        -8-
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metadata_filer: {"company-data": {"conformed-name": "ASPEN TECHNOLOGY INC /DE/", "cik": "0000929940", "assigned-sic": "7371", "irs-number": "042739697", "state-of-incorporation": "DE", "fiscal-year-end": "0630"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-42536", "film-number": "681570"}, "business-address": {"street1": "TEN CANAL PARK", "city": "CAMBRIDGE", "state": "MA", "zip": "02141", "phone": "6179491000"}, "mail-address": {"street1": "TEN CANAL PARK", "city": "CAMBRIDGE", "state": "MA", "zip": "02141"}}
text: 1
             As filed with the Securities and Exchange Commission on July 28, 2000
  
                                                        Registration No. 333-_____
  
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D.C. 20549
  
                                      FORM S-8
  
                            REGISTRATION STATEMENT UNDER
                             THE SECURITIES ACT OF 1933
  
                               ASPEN TECHNOLOGY, INC.
               (Exact Name of Registrant as Specified in Its Charter)
  
                                      Delaware
           (State or Other Jurisdiction of Incorporation or Organization)
  
                                     04-2739697
                        (I.R.S. Employer Identification No.)
  
                 Ten Canal Park, Cambridge, Massachusetts   02141
                 (Address of Principal Executive Offices) (Zip Code)
  
                      Petrolsoft Corporation Stock Option Plan
                              (Full Title of the Plan)
  
                                  Lawrence B. Evans
                  Chairman of the Board and Chief Executive Officer
                               Aspen Technology, Inc.
                                   Ten Canal Park
                           Cambridge, Massachusetts 02141
                       (Name and Address of Agent for Service)
  
                                   (617) 949-1000
            (Telephone Number, Including Area Code, of Agent For Service)
  
                           CALCULATION OF REGISTRATION FEE
  ------------------------------------------------------------------------------------------------------------------
                                                                   Proposed         Proposed
                                                                    Maximum          Maximum
              Title of Securities                  Amount       Offering Price  Aggregate Offering     Amount of
               To Be Registered               To Be Registered     Per Share          Price        Registration Fee
  ------------------------------------------------------------------------------------------------------------------
  Common Stock, $.10 par value..............       123,885         $11.36(1)     $1,407,333.60(1)      $371.54
  ------------------------------------------------------------------------------------------------------------------
  (1)  Calculated in accordance with Rule 457(h) under the Securities Act of 1933.
  2
  
  PART I. INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS
  
          The information required by Part I is included in documents sent or
  given to participants in the Petrolsoft Corporation Stock Option Plan pursuant
  to Rule 428(b)(1) of the Securities Act of 1933, as amended (the "Securities
  Act").
  
  PART II. INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
  
  Item 3. INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE
  
          The Registrant is subject to the informational and reporting
  requirements of Sections 13(a), 13(c), 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 filed with the
  Commission, are incorporated in this Registration Statement by reference:
  
          (1)  The Registrant's latest prospectus filed pursuant to Rule 424(b)
               under the Securities Act that contains audited financial statements
               for the Registrant's latest fiscal year for which such statements
               have been filed.
  
          (2)  All other reports filed pursuant to Section 13(a) or 15(d) of the
               Exchange Act since the end of the fiscal year covered by the
               prospectus referred to in (1) above.
  
          (3)  The description of the common stock of the Registrant, $.10 par
               value per share (the "Common Stock"), contained in the Registrant's
               registration statement on Form 8-A filed with the Commission under
               Section 12(g) of 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.
  
                                        -2-
  3
  
  Item 4. DESCRIPTION OF SECURITIES
  
          Not applicable.
  
  Item 5. INTERESTS OF NAMED EXPERTS AND COUNSEL
  
          Not applicable.
  
  Item 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS
  
          Article SEVENTH of the Registrant's Certificate of Incorporation, as
  amended (the "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 prohibits the elimination or limitation of liability of
  directors for breach of fiduciary duty.
  
          Article EIGHTH of the Certificate of Incorporation provides that a
  director or officer of the Registrant shall be indemnified by the Registrant
  against:
  
          (a)  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 or her by virtue
               of his or her position as a director or officer of the Registrant
               if he or she acted 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 or her conduct was unlawful
               and
  
          (b)  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 or her by virtue of his
               or her position as a director or officer of the Registrant if he or
               she 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
               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 or she 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 the dismissal of an
  action without prejudice, he or she 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
  or her request, provided that he or she undertakes to repay the amount advanced
  if it is ultimately determined that he or she 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 sixty 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 EIGHTH of the 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 is amended to expand the
  indemnification permitted to directors or officers the Registrant must indemnify
  those persons to the fullest extent permitted by such law as so amended.
  
          Section 145 of the Delaware General Corporation Law 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
  
                                        -3-
  4
  
  proceeding to which he or she 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 or she 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 or her 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.
  
          The Registrant maintains a directors' and officers' insurance policy
  that covers certain liabilities of directors and officers of the Registrant,
  including liabilities under the Securities Act of 1933. The Registrant maintains
  a general liability insurance policy that covers certain liabilities of
  directors and officers of the Registrant arising out of claims based on acts or
  omissions in their capacities as directors or officers.
  
  Item 7. EXEMPTION FROM REGISTRATION CLAIMED
  
          Not applicable.
  
  Item 8. EXHIBITS
  
          The following exhibits are filed as part of this Registration Statement:
  
          4.1  Certificate of Incorporation of the Registrant. Incorporated by
               reference to an exhibit to the Registrant's Form 8-K dated March
               12, 1998 (filed March 27, 1998).
  
          4.2  By-Laws of the Registrant. Incorporated by reference to an exhibit
               to the Registrant's Registration Statement on Form 8-A (filed on
               September 13, 1994), as amended by Amendment No. 1 thereto (filed
               on June 12, 1998).
  
          4.3  Rights Agreement dated as of October 9, 1997, between the
               Registrant and American Stock Transfer and Trust Company, as Rights
               Agent. Incorporated by reference to an exhibit to the Registrant's
               Registration Statement on Form 8-A (filed on October 10, 1997), as
               amended by Amendment No. 1 thereto (filed on June 12, 1998).
  
          4.4  Specimen certificate representing Rights to Purchase Series A
               Participating Cumulative Preferred Stock of Aspen Technology, Inc.
               Incorporated by reference to Exhibit B to the Rights Agreement
               referenced in Exhibit 4.3.
  
          4.5  Specimen certificate for the Registrant's common stock, $.10 par
               value. Incorporated by reference to an exhibit to the Registrant's
               Registration Statement on Form 8-A (filed on October 10, 1997), as
               amended by Amendment No. 1 thereto (filed on June 12, 1998) and
               incorporated herein by reference.
  
          4.6  Registrant's Petrolsoft Corporation Stock Option Plan.
  
          5.1  Opinion of Hale and Dorr LLP.
  
         23.1  Consent of Arthur Andersen LLP.
  
         23.2  Consent of Hale and Dorr LLP (included in Exhibit 5.1).
  
         24.1  Power of Attorney (included in the signature page of this
               Registration Statement).
  
  Item 9. UNDERTAKINGS
  
          The Registrant hereby undertakes:
  
          (1)  to file, during any period in which offers or sales are being made,
               a post-effective amendment to this Registration Statement to
               include any material information with respect to the plan of
               distribution not
  
                                        -4-
  5
  
               previously disclosed in the Registration Statement or any material
               change to such information 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; and
  
          (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 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 in 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 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 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, Massachusetts, on this twenty-fourth day
  of July, 2000.
  
                                            ASPEN TECHNOLOGY, INC.
  
                                            By: /s/ Lawrence B. Evans
                                                ----------------------------------
                                                Lawrence B. Evans
                                                Chief Executive Officer
  
                                        -6-
  7
  
                                  POWER OF ATTORNEY
  
       We, the undersigned officers and directors of Aspen Technology, Inc.
  hereby severally constitute and appoint Lawrence B. Evans and Lisa W. Zappala,
  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 behalf in our capacities as officers and
  directors to enable Aspen Technology, Inc. to comply with all requirements
  of the Securities and Exchange Commission, hereby ratifying and confirming our
  signatures as they may be signed by 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 indicated, as of July 21, 2000.
  NAME                                           TITLE
           ----                                           -----
  /s/ Lawrence B. Evans
  ___________________________________________________     Chairman of the Board and Chief Executive Officer
  Lawrence B. Evans                                       (principal executive officer)
  
  /s/ Lisa W. Zappala
  ___________________________________________________     Senior Vice President and Chief Financial Officer
  Lisa W. Zappala                                         (principal financial and accounting officer)
  
  /s/ Joseph F. Boston
  ___________________________________________________     Director
  Joseph F. Boston
  
  ___________________________________________________     Director
  Gresham T. Brebach, Jr.
  
  ___________________________________________________     Director
  Douglas R. Brown
  
  /s/ Stephen L. Brown
  ___________________________________________________     Director
  Stephen L. Brown
  
  /s/ /Stephen M. Jennings
  ___________________________________________________     Director
  Stephen M. Jennings
  
  /s/ Joan C. McArdle
  ___________________________________________________     Director
  Joan C. McArdle
  
  ___________________________________________________     Director
  Alison Ross
  -7-
  8
  
                                    EXHIBIT INDEX
  Exhibit
  Number                 Description
  -------                -----------
  4.1         Certificate of Incorporation of the Registrant. Incorporated by reference to an exhibit to the
                Registrant's Form 8-K dated March 12, 1998 (filed March 27, 1998).
  
    4.2         By-Laws of the Registrant. Incorporated by reference to an exhibit to the Registrant's Registration
                Statement on Form 8-A (filed on September 13, 1994), as amended by Amendment No. 1 thereto (filed
                on June 12, 1998).
  
    4.3         Rights Agreement dated as of October 9, 1997, between the Registrant and American Stock Transfer
                and Trust Company, as Rights Agent. Incorporated by reference to an exhibit to the Registrant's
                Registration Statement on Form 8-A (filed on October 10, 1997), as amended by Amendment No. 1
                thereto (filed on June 12, 1998).
  
    4.4         Specimen certificate representing Rights to Purchase Series A Participating Cumulative Preferred
                Stock of Aspen Technology, Inc. Incorporated by reference to Exhibit B to the Rights Agreement
                referenced in Exhibit 4.3.
  
    4.5         Specimen certificate for the Registrant's common stock, $.10 par value. Incorporated by reference to
                an exhibit to the Registrant's Registration Statement on Form 8-A (filed on October 10, 1997), as
                amended by Amendment No. 1 thereto (filed on June 12, 1998) and incorporated herein by reference.
  
    4.6         Registrant's Petrolsoft Corporation Stock Option Plan.
  
    5.1         Opinion of Hale and Dorr LLP.
  
   23.1         Consent of Arthur Andersen LLP.
  
   23.2         Consent of Hale and Dorr LLP (included in Exhibit 5.1).
  
   24.1         Power of Attorney (included in the signature page of this Registration Statement).
  -8-