content: <PAGE>
  
      As filed with the Securities and Exchange Commission on October 19, 2001
  
                                                        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                                             04-2739697
  (State or Other Jurisdiction of                            (I.R.S. Employer
  Incorporation or Organization)                            Identification No.)
  
  Ten Canal Park, Cambridge, Massachusetts                        02141
  (Address of Principal Executive Offices)                      (Zip Code)
  
                          1998 Employee Stock Purchase Plan
                              (Full Title of the Plan)
  
                                  Lawrence B. Evans
     Chairman of the Board of Directors, President 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)
  
  <TABLE>
  <CAPTION>
  
                           CALCULATION OF REGISTRATION FEE
  
  ====================================================================================================================
                                                    Proposed Maximum       Proposed Maximum
  Title of Securities         Amount to be        Offering Price Per     Aggregate Offering          Amount of
  to be  Registered            Registered                 Share                Price             Registration Fee
  --------------------------------------------------------------------------------------------------------------------
  <S>                       <C>                        <C>                  <C>                      <C>
  
  Common Stock, $0.10
  par value per share       2,000,000 shares            $11.82(1)           $23,640,000(1)           $5,910.00
  ====================================================================================================================
  </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
        October 15, 2001.
  
  
  
  <PAGE>
  
  
                       STATEMENT OF INCORPORATION BY REFERENCE
  
           This Registration Statement on Form S-8 incorporates by reference the
  contents of the Registration Statement on Form S-8 (File No. 333-03857) filed by
  the Registrant on January 20, 1998 relating to the Registrant's 1998 Employee
  Stock Purchase Plan, with the following exceptions of Part II Item 5 and Item 6
  thereof, which are amended and restated in their entirety as follows:
  
           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
  
  <PAGE>
  
  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 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.
  
  
  
  <PAGE>
  
                                     SIGNATURES
  
           Pursuant to the requirements of the Securities Act of 1933, the
  registrant certifies that it has reasonable grounds to believe that it meets all
  of the requirements for filing on Form S-8 and has duly caused this registration
  statement to be signed on its behalf by the undersigned, thereunto duly
  authorized, in the City of Cambridge, Massachusetts on this seventeenth day of
  October, 2001.
  
                                  Aspen Technology, Inc.
  
                                  By: /s/ Lawrence B. Evans
                                     ---------------------------------------------
                                     Lawrence B. Evans
                                     Chairman of the Board of Directors, President
                                     and Chief Executive Officer
  
                          POWER OF ATTORNEY AND SIGNATURES
  
           We, the undersigned officers and directors of Aspen Technology, Inc.,
  hereby severally constitute and appoint Lawrence B. Evans, Lisa W. Zappala and
  Michael J. Muscatello, 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 Aspen Technology, Inc. to
  comply with the provisions of the Securities Act of 1933, as amended, and all
  requirements of the Securities and Exchange Commission, hereby ratifying and
  confirming our signatures as they may be signed by our said attorneys, or any of
  them, to said registration statement and any and all amendments thereto.
  
           Pursuant to the requirements of the Securities Act of 1933, this
  registration statement has been signed by the following persons in the
  capacities on this seventeenth day of October, 2001.
  
  
               SIGNATURE                              TITLE
               ---------                              -----
  
  /s/ Lawrence B. Evans              Chairman of the Board of Directors, President
  ----------------------------       and Chief Executive Officer (Principal
  Lawrence B. Evans                  executive officer)
  
  /s/ Lisa W. Zappala                Senior Vice President and Chief Financial
  -----------------------------      Officer (Principal financial and
  Lisa W. Zappala                    accounting officer)
  
  
                                     Director
  -----------------------------
  Joseph F. Boston
  
  <PAGE>
  
  /s/ Gresham T. Brebach                Director
  -------------------------------
  Gresham T. Brebach
  
  
  /s/ Douglas R. Brown                  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
  
  
  <PAGE>
  
  
                                  INDEX TO EXHIBITS
  
  NUMBER       DESCRIPTION
  ------       -----------
  4.1(1)       Certificate of Incorporation of the Registrant
  
  4.2(2)       By-Laws of the Registrant
  
  4.3(2)       Rights Agreement dated as of October 9, 1997 between the Registrant
               and American Stock Transfer and Trust Company, as rights agent
  
  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 on the signature pages of this
               registration statement)
  ------------
  
  *        Filed herewith
  
  (1)      Previously filed with the Securities and Exchange Commission as an
           Exhibit to the Registrant's Form 8-K filed March 27, 1998 and
           incorporated herein by reference.
  
  (2)      Previously filed with the Securities and Exchange Commission as 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), and incorporated herein by reference.
metadata_documents: [{"type": "S-8", "sequence": "1", "filename": "b40738ats-8.txt", "description": "ASPEN TECHNOLOGY, INC.", "secsgml_size_bytes": 13053}]
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": "333-71874", "film-number": "1762300"}, "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: As filed with the Securities and Exchange Commission on October 19, 2001
  
                                                        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                                             04-2739697
  (State or Other Jurisdiction of                            (I.R.S. Employer
  Incorporation or Organization)                            Identification No.)
  
  Ten Canal Park, Cambridge, Massachusetts                        02141
  (Address of Principal Executive Offices)                      (Zip Code)
  
                          1998 Employee Stock Purchase Plan
                              (Full Title of the Plan)
  
                                  Lawrence B. Evans
     Chairman of the Board of Directors, President 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 Maximum       Proposed Maximum
  Title of Securities         Amount to be        Offering Price Per     Aggregate Offering          Amount of
  to be  Registered            Registered                 Share                Price             Registration Fee
  --------------------------------------------------------------------------------------------------------------------
  Common Stock, $0.10
  par value per share       2,000,000 shares            $11.82(1)           $23,640,000(1)           $5,910.00
  ====================================================================================================================
  (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
        October 15, 2001.
  STATEMENT OF INCORPORATION BY REFERENCE
  
           This Registration Statement on Form S-8 incorporates by reference the
  contents of the Registration Statement on Form S-8 (File No. 333-03857) filed by
  the Registrant on January 20, 1998 relating to the Registrant's 1998 Employee
  Stock Purchase Plan, with the following exceptions of Part II Item 5 and Item 6
  thereof, which are amended and restated in their entirety as follows:
  
           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 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.
  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 seventeenth day of
  October, 2001.
  
                                  Aspen Technology, Inc.
  
                                  By: /s/ Lawrence B. Evans
                                     ---------------------------------------------
                                     Lawrence B. Evans
                                     Chairman of the Board of Directors, President
                                     and Chief Executive Officer
  
                          POWER OF ATTORNEY AND SIGNATURES
  
           We, the undersigned officers and directors of Aspen Technology, Inc.,
  hereby severally constitute and appoint Lawrence B. Evans, Lisa W. Zappala and
  Michael J. Muscatello, 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 Aspen Technology, Inc. to
  comply with the provisions of the Securities Act of 1933, as amended, and all
  requirements of the Securities and Exchange Commission, hereby ratifying and
  confirming our signatures as they may be signed by our said attorneys, or any of
  them, to said registration statement and any and all amendments thereto.
  
           Pursuant to the requirements of the Securities Act of 1933, this
  registration statement has been signed by the following persons in the
  capacities on this seventeenth day of October, 2001.
  
               SIGNATURE                              TITLE
               ---------                              -----
  
  /s/ Lawrence B. Evans              Chairman of the Board of Directors, President
  ----------------------------       and Chief Executive Officer (Principal
  Lawrence B. Evans                  executive officer)
  
  /s/ Lisa W. Zappala                Senior Vice President and Chief Financial
  -----------------------------      Officer (Principal financial and
  Lisa W. Zappala                    accounting officer)
  
                                     Director
  -----------------------------
  Joseph F. Boston
  /s/ Gresham T. Brebach                Director
  -------------------------------
  Gresham T. Brebach
  
  /s/ Douglas R. Brown                  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
  INDEX TO EXHIBITS
  
  NUMBER       DESCRIPTION
  ------       -----------
  4.1(1)       Certificate of Incorporation of the Registrant
  
  4.2(2)       By-Laws of the Registrant
  
  4.3(2)       Rights Agreement dated as of October 9, 1997 between the Registrant
               and American Stock Transfer and Trust Company, as rights agent
  
  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 on the signature pages of this
               registration statement)
  ------------
  
  *        Filed herewith
  
  (1)      Previously filed with the Securities and Exchange Commission as an
           Exhibit to the Registrant's Form 8-K filed March 27, 1998 and
           incorporated herein by reference.
  
  (2)      Previously filed with the Securities and Exchange Commission as 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), and incorporated herein by reference.