<PAGE>   1

    AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON SEPTEMBER 9, 1996

                                                           FILE NO. 33-________

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

                       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)


                MASSACHUSETTS                                04-2739697
       (State Or Other Jurisdiction Of                    (I.R.S. Employer
       Incorporation Or Organization)                    Identification No.)

                       TEN CANAL PARK, CAMBRIDGE, MA 02141
               (Address of Principal Executive Offices) (Zip Code)

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

           ASPEN TECHNOLOGY, INC. 1995 EMPLOYEES' STOCK PURCHASE PLAN
             ASPEN TECHNOLOGY, INC. 1995 DIRECTORS STOCK OPTION PLAN
                  ASPEN TECHNOLOGY, INC. 1995 STOCK OPTION PLAN
                           (Full Titles of the Plans)

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

                                LAWRENCE B. EVANS
                     CHAIRMAN OF THE BOARD OF DIRECTORS AND
                             CHIEF EXECUTIVE OFFICER
                             ASPEN TECHNOLOGY, INC.
                                 Ten Canal Park
                               Cambridge, MA 02141
                     (Name and address of Agent for Service)



                                 (617) 577-0100
           Telephone Number, Including Area Code, of Agent for Service

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


                                    Copy to:

                             RICHARD M. HARTER, ESQ.
                            BINGHAM, DANA & GOULD LLP
                               150 Federal Street
                              Boston, MA 02110-1726
                                 (617) 951-8000


<TABLE>

                                                  CALCULATION OF REGISTRATION FEE
===================================================================================================================
<CAPTION>
                                                              PROPOSED           PROPOSED
                                           AMOUNT             MAXIMUM             MAXIMUM           AMOUNT OF
       TITLE OF EACH CLASS OF               TO BE          OFFERING PRICE        AGGREGATE         REGISTRATION
    SECURITIES TO BE REGISTERED          REGISTERED          PER SHARE*       OFFERING PRICE*          FEE
- -------------------------------------------------------------------------------------------------------------------
<S>                                       <C>                 <C>              <C>                  <C>           
Common Stock, $.10 par value .....        1,654,685           $65.87           $108,994,101         $37,584.17
===================================================================================================================

<FN>

*    The proposed maximum offering price has been calculated in accordance with
     the provisions of Rule 457(h) based on the average of the high and low
     prices reported in the consolidated reporting system on September 5, 1996.
     It is not known how many shares, if any, will be purchased upon exercise of
     options granted under the Plans or at what price such shares will be
     purchased.
</TABLE>




<PAGE>   2



                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents filed by Aspen Technology, Inc. (the
"Registrant") with the Securities and Exchange Commission (the "SEC") are hereby
incorporated by reference in this Registration Statement: (a) the Registrant's
Annual Report on Form 10-K for the fiscal year ended June 30, 1995; (b) all
reports previously filed by the Registrant pursuant to Section 13(a) or 15(d) of
the Securities Exchange Act of 1934, as amended (the "Exchange Act"), since the
end of the Registrant's 1995 fiscal year; and (c) the description of the Common
Stock contained in the Registrant's registration statement filed with the SEC
under Section 12(g) of the Exchange Act, including any amendment or report
filed for the purpose of updating such description.

         In addition, 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 indicate that all securities offered
hereby have been sold or which deregister all of such securities then remaining
unsold, shall be deemed to be incorporated by reference into this Registration
Statement and to be a part hereof from the date of filing of such documents.

ITEM 4.  DESCRIPTION OF SECURITIES

         Not applicable.

ITEM 5.  INTERESTS OF NAMED EXPERTS OR COUNSEL

         Richard M. Harter, Esq., a partner at the Registrant's legal counsel,
Bingham, Dana & Gould LLP, is the Clerk of the Registrant and owns a total of
10,000 shares of Common Stock of the Registrant.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS

         Section 67 of Chapter 156B of the Massachusetts General Laws provides a
statutory framework covering indemnification of directors and officers against
liabilities and expenses arising out of legal proceedings brought against them
by reason of their status or service as directors or officers. In addition,
Article VII of the Registrant's By-Laws provides for indemnification of
Directors, officers and employees of the Registrant. Section 67 and the
Registrant's By-Laws generally provide that a Director, officer or employee of
the Registrant shall be indemnified by the Registrant for all expenses and
liabilities of legal proceedings brought against him/her by reason of his/her
status or service as a Director, officer or employee unless the Director,
officer or employee is adjudged not to have acted in good faith in the
reasonable belief that his/her action was in the best interest of the Registrant
or, to the extent that such matter relates to service with respect to an
employee benefit plan, in the best interests of the participants or
beneficiaries of such plan. The Registrant's Restated Articles of Organization
also incorporate certain provisions permitted under the Massachusetts General
Laws relating to the liability of Directors. The provisions eliminate a
Director's liability for monetary damages for a breach of fiduciary duty,
including gross negligence, except in circumstances involving certain wrongful
acts, such as the breach of a Director's duty of loyalty or acts or omissions
not in good faith or which involve intentional misconduct or a knowing violation
of law or authorization of distributions in violation of the Restated Articles
of Organization or of loans to officers or Directors of the Registrant or any
transaction from which the Director derived an improper personal benefit. These
provisions do not eliminate a Director's duty of care. Moreover, the provisions
do not apply to claims against a Director for violations of certain laws,
including federal securities laws.



<PAGE>   3



ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED

         Not applicable.

ITEM 8.  EXHIBITS

         The following exhibits are filed as part of this Registration
Statement:

           4.1      Restated Articles of Organization of the Registrant,
                    incorporated by reference to Exhibit 3.1 to the Registration
                    Statement on Form S-1 of the Registrant (Registration No.
                    32-88734) filed with the SEC on January 29, 1995.

           4.2      By-Laws of Registrant, incorporated by reference to Exhibit
                    3.3 to the Registration Statement on Form S-1 of the
                    Registrant (Registration No. 33-83916) filed with the SEC on
                    September 13, 1994.

           4.3      The Registrant's 1995 Employees' Stock Purchase Plan

           4.4      The Registrant's 1995 Directors Stock Option Plan.

           4.5      The Registrant's 1995 Stock Option Plan

             5      Opinion and Consent of Bingham, Dana & Gould LLP, counsel to
                    the Registrant, with respect to the legality of the shares
                    being registered.

          23.1      Consent of Arthur Andersen LLP.

          23.2      Consent of Bingham, Dana & Gould LLP (included in Exhibit
                    5).

            24      Power of Attorney (included in signature page to
                    Registration Statement).

ITEM 9.  UNDERTAKINGS

         The undersigned Registrant hereby undertakes:

               (1)    To file, during any period in which offers or sales are
         being made, a post-effective amendment to this Registration Statement,
         to include any material information with respect to the plan of
         distribution not previously disclosed in this Registration Statement or
         any material change to such information in this Registration Statement;

               (2)    That, for the purpose of determining any liability under
         the Securities Act, each such post-effective amendment shall be deemed
         to be a new registration statement relating to the securities offered
         therein, and the offering of such securities at that time shall be
         deemed to be the initial bona fide offering thereof;

               (3)    To remove from registration by means of a post-effective
          amendment any of the securities being registered which remain unsold
          at the termination of the offering;

               (4)    That, for purposes of determining any liability under the
         Securities Act of 1933 (the "Securities Act"), each filing of the
         Registrant's annual report pursuant to Section 13(a) or 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 


<PAGE>   4


          therein, and the offering of such securities at that time shall be
          deemed to be the initial bona fide offering thereof; and

               (5)    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 SEC 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.



                  [Remainder of page intentionally left blank]




<PAGE>   5


                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, as amended,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Cambridge, Commonwealth of Massachusetts, on
this 5th day of September, 1995.

                                        ASPEN TECHNOLOGY, INC.


                                        By: /s/ Lawrence B. Evans
                                           ------------------------------------
                                                Lawrence B. Evans, Chairman


                                POWER OF ATTORNEY

         Each person whose signature appears below hereby appoints Lawrence B.
Evans, Mary A. Palermo, Joel B. Rosen and Sharon A. Turley and each of them
severally, acting alone and without the other, his/her true and lawful
attorney-in-fact with the authority to execute in the name of each such person,
and to file with the Securities and Exchange Commission, together with any
exhibits thereto and other documents therewith, any and all amendments
(including without limitation post-effective amendments) to this Registration
Statement on Form S-8 necessary or advisable to enable the Registrant to comply
with the Securities Act of 1933, as amended, and any rules, regulations and
requirements of the Securities and Exchange Commission in respect thereof, which
amendments may make such other changes in this Registration Statement as the
aforesaid attorney-in-fact executing the same deems appropriate.

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacity indicated on the 5th day of September, 1996.

         SIGNATURE                                TITLE
         ---------                                -----

/s/ Lawrence B. Evans            Chairman of the Board of Directors and Chief
- -----------------------------    Executive Officer (Principal Executive Officer)
    LAWRENCE B. EVANS                                

/s/ Mary A. Palermo              Executive Vice President (Principal Accounting
- -----------------------------    Officer and Principal Financial Officer)
    MARY A. PALERMO                                  

/s/ Joseph F. Boston             Director
- -----------------------------
    JOSEPH F. BOSTON

                                 Director
- -----------------------------
    GRESHAM T. BREBACH, JR.

/s/ Douglas R. Brown             Director
- -----------------------------
    DOUGLAS R. BROWN

/s/ Joan C. McArdle              Director
- -----------------------------
    JOAN C. MCARDLE

                                 Director
- -----------------------------
    ALISON ROSS

                                 Director
- -----------------------------
    WILLIAM C. ROUSSEAU




<PAGE>   6


<TABLE>

  
                                     INDEX TO EXHIBITS
<CAPTION>


EXHIBIT NUMBER                      DESCRIPTION                                     SEQUENTIAL PAGE NO.
- --------------                      -----------                                     -------------------

   <S>         <C>                                                                          <C>
    4.1        Restated Articles of Organization of the Registrant, incorporated
               by reference to Exhibit 3.1 to the Registration Statement on Form
               S-1 of the Registrant (Registration No. 32-88734) filed with the
               SEC on January 29, 1995.

    4.2        By-Laws of Registrant, incorporated by reference to Exhibit 3.3
               to the Registration Statement on Form S-1 of the Registrant
               (Registration No. 33-83916) filed with the SEC on September 13,
               1994.

    4.3        The Registrant's 1995 Employees' Stock Purchase Plan                          

    4.4        The Registrant's 1995 Directors Stock Option Plan.                           

    4.5        The Registrant's 1995 Stock Option Plan                                      

     5         Opinion and Consent of Bingham, Dana & Gould LLP with respect to
               the legality of the shares being registered.                                 

   23.1        Consent of Arthur Andersen LLP.                                              

   23.2        Consent of Bingham, Dana & Gould LLP (included in Exhibit 5).

    24         Power of Attorney (included in signature page to Registration
               Statement).
</TABLE>








<PAGE>   1

                                                                    Exhibit 4.3
                                                                    ----------- 

                             ASPEN TECHNOLOGY, INC.

                       1995 EMPLOYEES' STOCK PURCHASE PLAN

         1. DEFINITIONS. As used in this 1995 Employees' Stock Purchase Plan of
Aspen Technology, Inc., the following terms shall have the meanings respectively
assigned to them below:

          (a)  BENEFICIARY means the person designated as beneficiary on the
               Optionee's Membership Agreement or, if no such beneficiary is
               named, the person to whom the Option is transferred by will or
               under the applicable laws of descent and distribution.

          (b)  CODE means the Internal Revenue Code of 1986, as amended.

          (c)  COMMITTEE means a committee of the board of directors of the
               Company composed exclusively of disinterested directors.

          (d)  COMPANY means Aspen Technology, Inc., a Massachusetts
               corporation.

          (e)  COMPENSATION means annual compensation, including commissions,
               overtime and bonuses for the most recently completed calendar
               year.

          (f)  ELIGIBLE EMPLOYEE means a person who is eligible under the
               provisions of Section 7 to receive an Option as of a particular
               Grant Date.

          (g)  EXERCISE DATE means a date not more than 27 months after a Grant
               Date, as determined by the Committee, on which Options must, if
               ever, be executed.

          (h)  GRANT DATE means a date specified by the Committee on which

               Options are to be granted to Eligible Employees.

          (j)  MARKET VALUE means, as of a particular date, the value as
               determined by the Committee in accordance with applicable
               provisions of the Code and Treasury Department rulings and
               regulations thereunder or, if applicable, the closing price of
               the Stock reported by NASDAQ in The Wall Street Journal on such
               date.


<PAGE>   2


                                      -2-

          (k)  MEMBERSHIP AGREEMENT means an agreement whereby an Optionee
               authorizes the Company to withhold payroll deductions from his or
               her Compensation.

          (l)  OPTION means an option to purchase shares of Stock granted under
               the Plan.

          (m)  OPTIONEE means an Eligible Employee to whom an Option is granted.

          (n)  PLAN means this 1995 Employees' Stock Purchase Plan of the
               Company.

          (o)  RELATED CORPORATION means any corporation which is a parent
               corporation of the Company, as defined in Section 424(e) of the
               Code, and any corporation controlled by that parent corporation
               or the Company.

          (p)  STOCK means common stock, $0.10 par value, of the Company.

         2. PURPOSE OF THE PLAN. The Plan is intended to encourage ownership of
Stock by employees of the Company and to provide additional incentive for the
employees to promote the success of the business of the Company. It is intended
that the Plan shall be an "employee stock purchase plan" within the meaning of
Section 423 of the Code.

         3. TERM OF THE PLAN. The Plan shall become effective on December 18, 
1995. No option shall be granted under the Plan after November 30, 2005.

         4. ADMINISTRATION OF THE PLAN. The Plan shall be administered by the
Committee, which shall determine from time to time whether to grant Options
under the Plan, shall specify which dates shall be Grant Dates and Exercise
Dates, shall determine the fair market value of the Stock, and shall fix the
maximum percentage of each Optionee's Compensation which may be withheld for the
purpose of purchasing shares of Stock; PROVIDED, that, the maximum percentage
shall not exceed five percent. The Committee shall have authority to interpret
the Plan, to prescribe, amend and rescind rules and regulations relating to the
Plan, to determine the terms of Options granted under the Plan, and to make all
other determinations necessary or advisable for the administration of the Plan.



<PAGE>   3

                                      -3-


         5. TERMINATION AND AMENDMENT OF PLAN. The Committee may terminate or 
amend the Plan at any time; PROVIDED HOWEVER, that the Committee may not,
without approval by the holders of a majority of the shares of Stock, increase
the maximum number of shares of Stock purchasable under the Plan, change the
description of employees or classes of employees eligible to receive Options,
change the manner of determining the exercise price of Options, or extend the
period during which Options may be granted or exercised. No termination of or
amendment to the Plan may adversely affect the rights of an Optionee with
respect to any Option held by the Optionee as of the date of such termination or
amendment.

         6. SHARES OF STOCK SUBJECT TO THE PLAN. No more than an aggregate of
250,000 shares of Stock may be issued or delivered pursuant to the exercise of
Options granted under the Plan, subject to adjustments made in accordance with
Section 9.8. Shares to be delivered upon the exercise of Options may be either
shares of Stock which are authorized but unissued or shares of Stock held by the
Company in its treasury. If an Option expires or terminates for any reason
without having been exercised in full, the unpurchased shares subject to the
Option shall become available for other Options granted under the Plan. The
Company shall, at all items during which Options are outstanding, reserve and
keep available shares of Stock, sufficient to satisfy such Options, and shall
pay all fees and expenses incurred by the Company in connection there with. In
the event of any capital change in the outstanding Stock as contemplated by
Section 9.8, the number of shares of Stock reserved and kept available by the
Company shall be appropriately adjusted.

         7. PERSONS ELIGIBLE TO RECEIVE OPTIONS. Each employee of the Company 
or a specified Related Corporation shall be granted an Option on each Grant Date
on which such employee meets all of the following requirements:

          (a)  The employee has been employed by the Company and the Related
               Corporation for at least one month and is customarily so employed
               by the Company for at least twenty hours per week and for more
               than five months per calendar year.

          (b)  The employee will not, after grant of the Option, own stock
               possessing five percent or more of the total combined voting
               power or value of all classes of stock of the Company or of any
               Related Corporation. For purposes of this paragraph (b), the
               rules of Section 424(d) of the Code shall apply in determining
               the stock ownership of the employee, and stock which the employee


<PAGE>   4


                                      -4-

               may purchase under outstanding options shall be treated as stock
               owned by the employee.

          (c)  Upon grant of the Option, the employee's rights to purchase stock
               under all employee stock purchase plans (as defined in Section
               423(b) of the Code) of the Company and its Related Corporations
               will not accrue at a rate which exceeds $25,000 of fair market
               value of the stock (determined as of the Grant Date) for each
               calendar year in which such option is outstanding at any time.
               The accrual of rights to purchase stock shall be determined in
               accordance with Section 423(b)(8) of the Code.

         8.    DATES FOR GRANTING OPTIONS. Options shall be granted on each date
designated by the Committee as a Grant Date.

         9.    TERMS AND CONDITIONS OF OPTIONS.

          9.1  GENERAL. All Options granted on a particular Grant Date shall
               comply with the terms and conditions Set forth in Section 9.3
               through 9.12, and each Option shall be identical except as to the
               number of shares of Stock purchasable under the Option, which
               shall be determined in accordance with Section 9.2.

          9.2  NUMBER OF SHARES. The maximum number of shares of Stock which an
               Optionee shall be permitted to purchase shall be an amount equal
               to five percent of the Optionee's Compensation as of the Grant
               Date divided by 85 percent of the Market Value of the Stock as of
               the Grant Date.

          9.3  PURCHASE PRICE. The purchase price of shares of Stock shall be 85
               percent of the lesser of (a) the Market Value of the shares as of
               the Grant Date, or (b) the Market Value of the shares as of the
               Exercise Date, or such greater percentage as may be set by the
               Committee from time to time.

          9.4  RESTRICTIONS ON TRANSFER. Options may not be transferred
               otherwise than by will or under the laws of descent and
               distribution. An Option may not be exercised by anyone other than
               the Optionee during the lifetime of the Optionee. Shares of Stock
               may be sold or otherwise transferred by the Optionee without
               restriction subject to the provisions of Section 9.11 and the
               Stock Purchase Agreement that will be signed pursuant to Section
               9.10.


<PAGE>   5


                                      -5-

          9.5  EXPIRATION. Each Option shall expire at the close of business on
               the Exercise Date or on such earlier date as may result from the
               operation of Section 9.6.

          9.6  TERMINATION OF EMPLOYMENT OF OPTIONEE. If an Optionee ceases for
               any reason (other than death or retirement) to be continuously
               employed by the Company or a Related Corporation, whether due to
               voluntary severance, involuntary severance, transfer, or
               disaffiliation of the employer corporation with the Company, his
               or her Option shall immediately expire, and the Optionee's
               accumulated payroll deduction shall be returned by the Company
               without interest. For purposes of this Section 9.6, an Optionee
               shall be deemed to be employed throughout any leave of absence
               for military service, illness or other bona fide purpose which
               does not exceed the longer of ninety days of the period during
               which the Optionee's reemployment rights are guaranteed by
               statute or by contract. If the Optionee does not return to active
               employment prior to the termination of such period, his or her
               employment shall be deemed to have ended on the ninety-first day
               of such leave of absence.

          9.7  RETIREMENT OR DEATH OF OPTIONEE. If an Optionee retires or dies,
               the employee or in the case of death, his or her Beneficiary,
               shall be entitled to withdraw the Optionee's accumulated payroll
               deductions without interest or to purchase shares on the Exercise
               Date to the extent that the Optionee would be so entitled had he
               or she continued to be employed by the Company. The number of
               shares purchasable shall be limited by the amount of the
               Optionee's accumulated payroll deductions as of the date of his
               or her retirement or death. Accumulated payroll deductions shall
               be applied by the Company toward the purchase of shares only if
               the Optionee or Beneficiary submits to the Company a Stock
               Purchase Agreement pursuant to Section 9.10. Accumulated payroll
               deductions not withdrawn or applied to the purchase of shares
               shall be delivered by the Company to the Optionee or Beneficiary
               without interest within a reasonable time after the Exercise
               Date.

          9.8  CAPITAL CHANGES AFFECTING THE STOCK. In the event that, between
               the Grant Date and the Exercise Date of an Option, a stock
               dividend is paid or becomes payable in respect of the Stock or
               there occurs a split up or contraction in the number of shares of
               Stock, the number of shares for which the Option may thereafter



<PAGE>   6


                                      -6-

               be exercised and the price to be paid for each such share shall
               be proportionately adjusted. In the event that, after the Grant
               Date, there occurs a reclassification or change of outstanding
               shares of the Stock or a consolidation or merger of the Company
               with or into another corporation or a sale or conveyance,
               substantially as a whole, of the property of the Company, the
               Optionee shall be entitled on the Exercise Date to receive shares
               of Stock or other securities equivalent in kind and value to the
               shares of stock he or she would have held if he or she had
               exercised the Option in full immediately prior to such
               reclassification, change, consolidation, merger, sale or
               conveyance and had continued to hold such shares (together with
               all other shares and securities thereafter issued in respect
               thereof) until the Exercise Date. In the event that there is to
               occur a recapitalization involving an increase in the par value
               exceeding the exercise price under an outstanding Option, the
               Company shall notify the Optionee of such proposed
               recapitalization immediately upon its being recommended to the
               Company's shareholders, after which the Optionee shall have the
               right to exercise his or her Option prior to such
               recapitalization; if the Optionee fails to exercise the Option
               prior to recapitalization, the exercise price under the Option
               shall be appropriately adjusted. In the event that, after the
               Grant Date, there occurs a dissolution or liquidation of the
               Company, except pursuant to a transaction to which Section 424(a)
               of the Code applies, each Option to purchase Stock of the Company
               to be dissolved or liquidated shall terminate, but the Optionee
               holding such Option shall have the right toe exercise his or her
               Option prior to such dissolution or liquidation.

          9.9  PAYROLL DEDUCTIONS. An Optionee may purchase shares under his or
               her Option by completing and returning to the Company a
               Membership Agreement indicating the amount of his or her
               Compensation, not to exceed five percent, which is to be withheld
               each pay period. A Membership Agreement may continue from the
               period following one Grant Date to the periods following
               subsequent Grant Dates until revoked by the Optionee. The
               Optionee may withdraw any or all of his or her accumulated
               payroll deductions on the Exercise Date or such earlier date as
               is permitted by the Membership Agreement by submitting a written
               request therefor to the Company no later than two weeks prior to
               the date on which the withdrawal will be effective.


<PAGE>   7


                                      -7-


          9.10 EXERCISE OF OPTIONS. On the Exercise Date the Optionee may
               purchase the number of shares purchasable by his or her
               accumulated payroll deduction, provided that:

               (a)  The number of shares of Stock purchasable shall not exceed
                    the number of shares the Optionee is entitled to purchase
                    pursuant to Section 9.2.

               (b)  If the number of shares purchasable includes a fraction,
                    that number shall be adjusted to the next smaller whole
                    number and the purchase price shall be adjusted accordingly.

               The Optionee may elect to purchase shares of Stock from his or
               her Base Amount by completing and returning to the Company a
               Stock Purchase Agreement no later than two weeks prior to the
               Exercise Date. If the Company does not receive a Stock Purchase
               Agreement from the Optionee by such date, accumulated payroll
               deductions will be returned on the Exercise Date without
               interest.

          9.11 DELIVERY OF STOCK. Within a reasonable time after the Exercise
               Date, the Company shall deliver or cause to be delivered to the
               Optionee a certificate or certificates for the number of shares
               purchased by the Optionee. At the time of any exercise of any
               option, the Company may, if it shall deem it necessary or
               desirable for any reason connected with any law or applicable
               regulation of the Securities and Exchange Commission or state
               securities laws, require the Optionee or a transfer of the
               Optionee's rights to represent in writing to the Company that it
               is such person's then intention to acquire the Stock for
               investment and not with a view to the distribution thereof. Such
               representation shall lapse when in the view of the Company it is
               no longer necessary under the law or regulations in existence at
               the time. The Company shall have the right to place a legend on
               all certificates that the shares represented by such certificates
               may not be transferred unless a Registration Statement with
               respect to these shares is effective under the Securities Act of
               1933, as amended, or unless the Company shall receive an opinion
               of counsel satisfactory to it that transfer will not violate said
               act or regulations thereunder. If any law or applicable
               regulation of the Securities and Exchange Commission or other
               body having jurisdiction in the premises shall require that the
               Company or the Optionee take any action in connection with the


<PAGE>   8


                                      -8-


               shares being purchased under the Option, delivery of the
               certificate or certificates for such shares shall be postponed
               until the necessary action shall have been completed. The
               Optionee shall have no rights as a shareholder in respect of
               shares for which he or she has not received a certificate.

          9.12 RETURN OF ACCUMULATED PAYROLL DEDUCTIONS. In the event that the
               Optionee or the Beneficiary is entitled to the return of
               accumulated payroll deductions, whether by reason of voluntary
               withdrawal, termination of employment, retirement, death, or in
               the event that accumulated payroll deductions exceed the price of
               share purchased, such amount shall be returned without interest
               within a reasonable time after the Exercise Date or such earlier
               date as is permitted by the Membership Agreement. Payroll
               deductions shall be returned by the Company to the Optionee or
               the Beneficiary, as the case may be. An Optionee's Membership
               Agreement may specify that amounts exceeding the purchase price
               will be carried forward to the next option period under the Plan.





<PAGE>   1
                                                                    Exhibit 4.4
                                                                    -----------

                             ASPEN TECHNOLOGY, INC.

                        1995 DIRECTORS STOCK OPTION PLAN

     1.  DEFINITIONS. As used in this 1995 Directors Stock Option Plan of Aspen
Technology, Inc., the following terms shall have the following meanings:


          1.1 CHANGE IN CORPORATE CONTROL means the date on which any
     individual, corporation, partnership or other person or entity (together
     with its "Affiliates" and "Associates," as defined in Rule 12b-2 under the
     Securities Exchange Act of 1934) "beneficially owns" (as defined in Rule
     13d-3 under the Securities Exchange Act of 1934) in the aggregate 20% or
     more of the outstanding shares of capital stock of the Company entitled to
     vote generally in the election of directors of the Company.

          1.2  CODE means the Internal Revenue Code of 1986, as amended.

          1.3  COMPANY means Aspen Technology, Inc., a Massachusetts 
     corporation.

          1.4  FAIR MARKET VALUE at any date means the closing price on the
     NASDAQ National Market on the last business day before that date.

          1.5  GRANT DATE means the date on which an Option is granted, as
     specified in Sections 5 and 6.

          1.6  OPTION means an option to purchase shares of the Stock granted
     under the Plan.

          1.7  OPTION AGREEMENT means an agreement between the Company and an
     Optionee, setting forth the terms
 and conditions of an Option.

          1.8  OPTION PRICE means the price paid by an Optionee for an Option
     under this Plan.

          1.9  OPTION SHARE means any share of Stock of the Company transferred
     to an Optionee upon exercise of an Option pursuant to this Plan.



<PAGE>   2

                                      -2-

               1.10 OPTIONEE means a person to whom an Option shall have been 
     granted under the Plan.

               1.11 PLAN means this 1995 Directors Stock Option Plan of the 
     Company.

               1.12 STOCK means common stock, $.10 par value, of the Company.

     2.  PURPOSE. This 1995 Directors Stock Option Plan is intended to encourage
ownership of the Stock by non-employee directors of the Company and to provide
additional incentive for them to promote the success of the Company's business.

     3.  TERM OF THE PLAN. Options under the Plan may be granted not later than
November 30, 2005.

     4.  STOCK SUBJECT TO THE PLAN. At no time shall the number of shares of the
Stock then outstanding which are attributable to the exercise of Options granted
under the Plan plus the number of shares then issuable upon exercise of
outstanding options granted under the Plan exceed 120,000 shares, SUBJECT,
HOWEVER, to the provisions of Section 11 of the Plan. Shares to be issued upon
the exercise of Options granted under the Plan may be either authorized but
unissued shares or shares held by the Company in its treasury. If any Option
expires or terminates for any reason without having been exercised in full, the
shares not purchased thereunder shall again be available for Options thereafter
to be granted.

     5.  FIRST GRANTS TO CERTAIN DIRECTORS. Each individual who was not, within
the 12 months preceding his or her first election to the Board of Directors,
either an officer or employee of the Company or any subsidiary of the Company
and who is serving as a director immediately after the 1995 Annual Meeting of
Stockholders or who is first elected to the Board of Directors during the term
of the Plan (whether elected at an annual or special stockholders' meeting or by
action of the Board of Directors) shall be granted, on the date of the 1995
Annual Meeting or such later election an Option to purchase 12,000 shares of
Stock. Each Option shall (i) have an exercise price equal to 100% of the Fair
Market Value of the Stock on the Grant Date, and (ii) become exercisable in 12
quarterly installments, beginning with the last day of the calendar quarter
following the Grant Date, but only if the Optionee remains a director of the
Company on the respective dates. The Option Period shall be ten years from the
Grant Date.


<PAGE>   3

                                      -3-

     6.  SUBSEQUENT GRANTS TO CERTAIN DIRECTORS. Each individual who continues 
as a non-employee director following any Annual Meeting of Stockholders of the
Company shall be granted, on the date of that Annual Meeting of Stockholders, an
Option to purchase 4,000 shares of Stock. Each Option shall (i) have an Exercise
Price equal to 100% of the Fair Market Value of the Stock on the Grant Date and
(ii) become exercisable in four quarterly installments, beginning with the third
anniversary of the Grant Date, but only if the Optionee remains a director of
the Company on the respective dates. The Option Period shall be ten years from
the Grant Date.

     7.  EXERCISE OF OPTION. An Option may be exercised only by giving written
notice, in the manner provided in Section 15 hereof, specifying the number of
shares as to which the Option is being exercised, accompanied by (a) full
payment for such shares in the form of check or bank draft payable to the order
of the Company, or (b) certificates representing shares of the Stock with a
current Fair Market Value equal to the Option Price of the shares to be
purchased, or (c) irrevocable instructions to a brokerage firm to sell a
sufficient number of the Option Shares to generate the full exercise price and
to pay over to the Company such proceeds of sale. Receipt by the Company of such
notice and payment shall constitute the exercise of the Option or a part
thereof. The Company shall thereafter deliver or cause to be delivered to the
Optionee a certificate or certificates for the number of shares then being
purchased by the Optionee. Such shares shall be fully paid and nonassessable. If
any law or applicable regulation of the Securities and Exchange Commission or
other body having jurisdiction in the premises shall require the Company or the
Optionee to take any action in connection with shares being purchased upon
exercise of the option, exercise of the option and delivery of the certificate
or certificates for such shares shall be postponed until completion of the
necessary action, which shall be taken at the Company's expense.

     8.  TRANSFERABILITY OF OPTIONS. Options shall not be transferable, 
otherwise than by will or the laws of descent and distribution, and may be
exercised during the life of the Optionee only by the Optionee.

     9.  STOCK PURCHASE AGREEMENT Each Optionee exercising an option, at the
request of the Company, will be required to sign a Stock Purchase Agreement
representing in form satisfactory to counsel for the Company that he or she will
not transfer, sell or otherwise dispose of the Option Shares at any time
purchased by him or her, upon the exercise of any portion of the Option, in a
manner which would violate the Securities Act of 1933, as amended, and the
regulations of the Securities and Exchange Commission thereunder; and the
Company may, at its discretion, make a notation on any certificates issued upon
exercise of options to the effect that such certificate may not be transferred
except after receipt by the Company of an opinion of 


<PAGE>   4

                                      -4-

counsel satisfactory to it to the effect that such transfer will not violate
such Act and such regulations, and may issue "stop transfer" instructions to its
transfer agent, if any, and make a "stop transfer" notation on its books as
appropriate. Such Stock Purchase Agreement shall include such other provisions
as the Committee may determine are appropriate.

     10. TERMINATION OF SERVICE. In the event that the Optionee's service 
as a director ends for any reason other than death, the Option, to the extent
exercisable at termination, may be exercised by the Optionee at any time within
30 days after termination unless terminated earlier by its terms. If termination
of service results from the death of the Optionee, the Option, to the extent
exercisable at the date of death, may be exercised by the person to whom the
Option is transferred by will or the applicable laws of descent and
distribution, at any time within 12 months after the date of death, unless
terminated earlier by its terms.

     11. ADJUSTMENT OF NUMBER OF SHARES. Each Option Agreement shall provide
that in the event of any capital adjustments including stock splits, stock
contractions, stock dividends, reclassifications, exchanges and substitutions,
occurring after the date of the option and prior to the exercise in full of the
option, the number of shares for which the option may be exercised and the price
per share shall be proportionately adjusted and in the event of any resulting
changes in the outstanding Stock, the number of the Stock available for the
purpose of the Plan as stated in Section 4 hereof shall be correspondingly
adjusted.

     12. STOCK RESERVED. The Company shall at all times during the term of the
Option reserve and keep available such number of shares of the Stock as will be
sufficient to satisfy the requirements of this Plan and shall pay all fees and
expenses necessarily incurred by the Company in connection therewith.

     13. LIMITATION OF RIGHTS IN THE OPTION SHARES. An Optionee shall not be
deemed for any purpose to be a stockholder of the Company with respect to any of
the Option Shares except to the extent that the Option shall have been exercised
with respect thereto and, in addition, a certificate shall have been issued
therefor and delivered to the Optionee.

     14. TERMINATION AND AMENDMENT OF THE PLAN. The Board of Directors of the
Company may at any time terminate the Plan or make such amendment to the Plan as
it shall deem advisable, provided that, except as provided in Section 11, it may
not, without the approval by the holders of a majority of the Stock, change the
classes of persons eligible to receive Options, increase the maximum number of
shares available for option under the Plan or extend the period during which
Options may be granted or exercised and it may not 


<PAGE>   5


                                      -5-

amend the Plan more than once in any six-month period except to the extent
necessary to comply with applicable Federal income tax laws and regulations. No
termination or amendment of the Plan may, without the consent of the Optionee to
whom any Option shall theretofore have been granted, adversely affect the rights
of such Optionee under such Option. The Company may also, in its discretion,
permit any option to be exercised prior to the date on which it vests.

     15. NOTICES. Any communication or notice required or permitted to be given
under the Plan shall be in writing, and mailed by registered or certified mail
or delivered in hand, if to the Company, to its Chief Financial Officer at Ten
Canal Park, Cambridge, MA 02141 and, if to the Optionee, to the address as the
Optionee shall last have furnished to the Company.





<PAGE>   1
                                                                    Exhibit 4.5
                                                                    -----------


                             ASPEN TECHNOLOGY, INC.

                             1995 STOCK OPTION PLAN


     1.   DEFINITIONS. As used in this 1995 Stock Option Plan of Aspen 
Technology, Inc., the following terms shall have the following meanings:

          1.1 CHANGE IN CORPORATE CONTROL means the date on which any
     individual, corporation, partnership or other person or entity (together
     with its "Affiliates" and "Associates," as defined in Rule 12b-2 under the
     Securities Exchange Act of 1934) "beneficially owns" (as defined in Rule
     13d-3 under the Securities Exchange Act of 1934) in the aggregate 20% or
     more of the outstanding shares of capital stock of the Company entitled to
     vote generally in the election of directors of the Company.

          1.2 CODE means the Internal Revenue Code of 1986, as amended.

          1.3 COMMITTEE means the Compensation Committee of the Company's Board
     of Directors.

          1.4 COMPANY means Aspen Technology, Inc., a Massachusetts corporation.

          1.5 FAIR MARKET VALUE means the value of a share of Stock of the
     Company on any date as determined by the Committee.

          1.6 GRANT DATE means the date on which an Option is granted, as
     specified in Section 7.

          1.7 INCENTIVE OPTION means an option which qualifies for tax treatment
     under Section 422 of the Code.

          1.8 MAJOR SHAREHOLDER means a person who,
 within the meaning of
     Section 422(b)(6) of the Code, is deemed to own stock possessing more than
     10% of the total combined voting power of all classes of stock of the
     Company (or of its parent or subsidiary corporations).




<PAGE>   2


                                      -2-

          1.9  OPTION means an option to purchase shares of the Stock granted
     under the Plan.

          1.10 OPTION AGREEMENT means an agreement between the Company and an
     Optionee, setting forth the terms and conditions of an Option.

          1.11 OPTION PRICE means the price paid by an Optionee for an Option
     under this Plan.

          1.12 OPTION SHARE means any share of Stock of the Company transferred
     to an Optionee upon exercise of an Option pursuant to this Plan.

          1.13 OPTIONEE means a person eligible to receive an Option, as
     provided in Section 6, to whom an Option shall have been granted under the
     Plan.

          1.14 PLAN means this 1995 Stock Option Plan of the Company.

          1.15 RELATED CORPORATION means a Parent Corporation or a Subsidiary
     Corporation, each as defined in Section 424 of the Code.

          1.16 STOCK means common stock, $.10 par value, of the Company.

     2.   PURPOSE. This 1995 Stock Option Plan is intended to encourage 
ownership of the Stock by key employees and key advisors of the Company and its
Related Corporations and to provide additional incentive for them to promote the
success of the Company's business. The Plan is intended to be an incentive stock
option plan within the meaning of Section 422 of the Code, but not all the
Options must be Incentive Options.

     3.   TERM OF THE PLAN. Options under the Plan may be granted not later than
November 30, 2005.

     4.   STOCK SUBJECT TO THE PLAN. Subject to the provisions of Section 16 of
the Plan, the number of shares of the Stock attributable to the exercise of
Options granted under the Plan plus the number of shares then issuable upon
exercise of outstanding options granted under the Plan shall at no time exceed
800,000 increased automatically at each of July 1, 1996 and July 1, 1997 by an


<PAGE>   3


                                      -3-

amount equal to 5% of the Stock outstanding on the preceding June 30. Unless and
until the Plan is amended, however, at no time may the number of shares
purchaseable under Options which are Incentive Options exceed 2 million shares.
Shares to be issued upon the exercise of Options granted under the Plan may be
either authorized but unissued shares or shares held by the Company in its
treasury. If any Option expires or terminates for any reason without having been
exercised in full, the shares not purchased thereunder shall again be available
for Options thereafter to be granted.

     5.   ADMINISTRATION. The Plan shall be administered by the Committee. 
Subject to the provisions of the Plan, the Committee shall have complete
authority, in its discretion, to make the following determinations with respect
to each Option to be granted by the Company: (a) the key employee or key advisor
to receive the Option; (b) the time of granting the Option; (c) the number of
shares subject thereto; (d) the Option Price; (e) the Option period; and (f) if
the Optionee is an employee, whether the Option is an Incentive Option. In
making such determinations, the Committee may take into account the nature of
the services rendered by the key employees and key advisors, their present and
potential contributions to the success of the Company and its Related
Corporations, and such other factors as the Committee in its discretion shall
deem relevant. Subject to the provisions of the Plan, the Committee shall also
have complete authority to interpret the Plan, to prescribe, amend and rescind
rules and regulations relating to it, to determine the terms and provisions of
the respective Option Agreements (which need not be identical), and to make all
other determinations necessary or advisable for the administration of the Plan.
The Committee's determinations on the matters referred to in this Section 5
shall be conclusive.

     6.   ELIGIBILITY. An Option may be granted only to a key employee or key
advisor of one or more of the Company and its Related Corporations. A director
of one or more of the Company and its Related Corporations who is not also an
employee of one or more of the Company and its Related Corporations shall not be
eligible to receive an Option. A Major Shareholder shall be eligible to receive
an Incentive Option only if the Option Price is at least 110% of the Fair Market
Value on the Grant Date and only if the Incentive Option expires, to the extent
not theretofore exercised, on the fifth anniversary of the Grant Date.

     7.   TIME OF GRANTING OPTIONS. The granting of an Option shall take place 
at the time specified by the Committee. Only if expressly so provided by the
Committee, shall the Grant Date be the date on which an Option Agreement shall
have been duly executed and delivered by the Company and the Optionee.


<PAGE>   4


                                      -4-

     8.   OPTION PRICE. The Option Price under each Incentive Option shall be 
not less than 100% of the Fair Market Value of the Stock on the Grant Date
except that the Option Price under an Incentive Option granted to a Major
Shareholder must be not less than 110% of the Fair Market Value.

     9.   OPTION PERIOD. No Option may be exercised later than the tenth
anniversary of the Grant Date or, for an Incentive Option granted to a Major
Shareholder, the fifth anniversary of the Grant Date. Unless the Committee
otherwise determines, all Options granted hereunder shall permit the Optionee to
purchase, cumulatively, one-sixteenth of the Option Shares at the end of each
calendar quarter following the Grant Date. Upon a Change in Corporate Control,
each outstanding Option shall immediately become fully exercisable.

     10.  MAXIMUM SIZE OF OPTION. No person shall be granted Options to purchase
more than 500,000 shares of Stock. To the extent that the aggregate Fair Market
Value of Stock for which an Incentive Option becomes exercisable by an Optionee
for the first time in any calendar year exceeds $100,000, the Option shall be
treated as a nonstatutory option, and not an Incentive Option. For purposes of
this Section 10, all Options granted to an Optionee by the Company shall be
considered in the order in which they were granted, and the Fair Market Value
shall be determined as of the Grant Dates.

     11.  EXERCISE OF OPTION. An Option may be exercised only by giving written
notice, in the manner provided in Section 20 hereof, specifying the number of
shares as to which the Option is being exercised, accompanied by (a) full
payment for such shares in the form of check or bank draft payable to the order
of the Company, or (b) certificates representing shares of the Stock with a
current Fair Market Value equal to the Option Price of the shares to be
purchased, or (c) irrevocable instructions to a brokerage firm to sell a
sufficient number of the Option Shares to generate the full exercise price plus
all applicable withholding taxes and to pay over to the Company such proceeds of
sale. Receipt by the Company of such notice and payment shall constitute the
exercise of the Option or a part thereof. The Company shall thereafter deliver
or cause to be delivered to the Optionee a certificate or certificates for the
number of shares then being purchased by the Optionee. Such shares shall be
fully paid and nonassessable. If any law or applicable regulation of the
Securities and Exchange Commission or other body having jurisdiction in the
premises shall require the Company or the Optionee to take any action in
connection with shares being purchased upon exercise of the option, exercise of
the option and delivery of the certificate or certificates for such shares shall
be postponed until completion of the necessary action, which shall be taken at
the Company's expense.


<PAGE>   5


                                      -5-

     12.  NOTICE OF DISPOSITION OF STOCK PRIOR TO EXPIRATION OF SPECIFIED 
HOLDING PERIOD. The Company may require that the person exercising an Incentive
Option give a written representation to the Company, satisfactory in form and
substance to its counsel and upon which the Company may reasonably rely, that he
or she will report to the Company any disposition of shares purchased upon
exercise prior to the expiration of the holding periods specified by Section
422(a)(1) of the Code. If and to the extent that the disposition imposes upon
the Company federal, state, local or other withholding tax requirements, or any
such withholding is required to secure for the Company an otherwise available
tax deduction, the Company shall have the right to require that the person
making the disposition remit to the Company an amount sufficient to satisfy
those requirements.

     13.  TRANSFERABILITY OF OPTIONS. Options shall not be transferable,
otherwise than by will or the laws of descent and distribution, and may be
exercised during the life of the Optionee only by the Optionee.

     14.  STOCK PURCHASE AGREEMENT Each Optionee exercising an option, at the
request of the Company, will be required to sign a Stock Purchase Agreement
representing in form satisfactory to counsel for the Company that he or she will
not transfer, sell or otherwise dispose of the Option Shares at any time
purchased by him or her, upon the exercise of any portion of the Option, in a
manner which would violate the Securities Act of 1933, as amended, and the
regulations of the Securities and Exchange Commission thereunder; and the
Company may, at its discretion, make a notation on any certificates issued upon
exercise of options to the effect that such certificate may not be transferred
except after receipt by the Company of an opinion of counsel satisfactory to it
to the effect that such transfer will not violate such Act and such regulations,
and may issue "stop transfer" instructions to its transfer agent, if any, and
make a "stop transfer" notation on its books as appropriate. Such Stock Purchase
Agreement shall include such other provisions as the Committee may determine are
appropriate.

     15.  TERMINATION OF EMPLOYMENT. In the event that the Optionee's employment
is terminated for any reason other than death or the Optionee's employer is no
longer the Company or a Related Corporation, the Option, to the extent
exercisable at termination, may be exercised by the Optionee at any time within
30 days after termination unless terminated earlier by its terms. If termination
results from the death of the Optionee, the Option, to the extent exercisable at
the date of death, may be exercised by the person to whom the Option is
transferred by will or the applicable laws of descent and distribution, at any
time within 12 months after the date of death, unless terminated earlier by its
terms. Military or sick leave shall not be deemed a termination of employment
provided that it does not exceed the longer of 90 days or the 


<PAGE>   6


                                      -6-

period during which the absent employee's re-employment rights are guaranteed by
statute or by contract.

     16.  ADJUSTMENT OF NUMBER OF SHARES. Each Option Agreement shall provide
that in the event of any capital adjustments including stock splits, stock
contractions, stock dividends, reclassifications, exchanges and substitutions,
occurring after the date of the option and prior to the exercise in full of the
option, the number of shares for which the option may be exercised and the price
per share shall be proportionately adjusted and in the event of any resulting
changes in the outstanding Stock, the number of shares of the Stock available
for the purpose of the Plan as stated in Section 4 hereof shall be
correspondingly adjusted. 

     17.  STOCK RESERVED. The Company shall at all times during the term of the
Option reserve and keep available such number of shares of the Stock as will be
sufficient to satisfy the requirements of this Plan and shall pay all fees and
expenses necessarily incurred by the Company in connection therewith.

     18.  LIMITATION OF RIGHTS IN THE OPTION SHARES. An Optionee shall not be
deemed for any purpose to be a stockholder of the Company with respect to any of
the Option Shares except to the extent that the Option shall have been exercised
with respect thereto and, in addition, a certificate shall have been issued
therefor and delivered to the Optionee.

     19.  TERMINATION AND AMENDMENT OF THE PLAN. The Board of Directors of the
Company may at any time terminate the Plan or make such amendment to the Plan as
it shall deem advisable, provided that, except as provided in Section 16, it may
not, without the approval by the holders of a majority of the Stock, change the
classes of persons eligible to receive Options, increase the maximum number of
shares available for option under the Plan or extend the period during which
Options may be granted or exercised. No termination or amendment of the Plan
may, without the consent of the Optionee to whom any Option shall theretofore
have been granted, adversely affect the rights of such Optionee under such
Option. The Company may also, in its discretion, permit any option to be
exercised prior to the date on which it vests.

     20.  NOTICES. Any communication or notice required or permitted to be given
under the Plan shall be in writing, and mailed by registered or certified mail
or delivered in hand, if to the Company, to its Chief Financial Officer at Ten
Canal Park, Cambridge, MA 02141 and, if to the Optionee, to the address as the
Optionee shall last have furnished to the Company.





<PAGE>   1
                                                                      Exhibit 5
                                                                      ---------


                                September 9, 1996


Aspen Technology, Inc.
Ten Canal Park
Cambridge, Massachusetts  02141

Ladies and Gentlemen:

         We have acted as counsel for Aspen Technology, Inc., a Massachusetts
corporation (the "Company"), in connection with the Company's Registration
Statement on Form S-8 proposed to be filed with the Securities and Exchange
Commission on or about September 9, 1996 (the "Registration Statement").

         The Registration Statement covers the registration of 1,654,685 shares
of common stock, par value $.10 per share, of the Company (the "Shares"), which
are to be issued by the Company upon exercise of stock options granted or to be
granted pursuant to the Company's 1995 Stock Option Plan, 1995 Directors Stock
Option Plan, and 1995 Employees' Stock Purchase Plan (collectively, the
"Plans").

         We have reviewed the corporate proceedings of the Company with respect
to the authorization of the Plans and the issuance of the Shares thereunder. We
have also examined and relied upon originals or copies of such agreements,
instruments, corporate records, certificates, and other documents as we have
deemed necessary or appropriate as a basis for the opinions hereinafter
expressed. In our examination, we have assumed the genuineness
 of all
signatures, the conformity to the originals of all documents reviewed by us as
copies, the authenticity and completeness of all original documents reviewed by
us in original or copy form, and the legal competence of each individual
executing any document.

         We further assume that all Shares issued upon exercise of options
granted or to be granted pursuant to the Plans will be issued in accordance with
the terms of such options and the Plans.

         Subject to the limitations set forth below, we have made such
examination of law as we have deemed necessary for the purposes of this opinion.
This opinion is limited solely to the Massachusetts Business Corporation Law.


<PAGE>   2



Aspen Technology, Inc.
September 9, 1996
Page 2



         Based upon and subject to the foregoing, we are of the opinion that the
Shares, when issued and delivered upon the exercise of options duly granted
pursuant to the Plans and against the payment of the purchase price or exercise
price therefor as provided in the Plans and the instrument evidencing the
relevant grant, will be validly issued, fully paid, and non-assessable.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                            Very truly yours,

                                            /s/ Bingham, Dana & Gould LLP


                                            BINGHAM, DANA & GOULD LLP






<PAGE>   1
                                                                   Exhibit 23.1
                                                                   ------------


                    CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

As independent public accountants, we hereby consent to (i) the incorporation by
reference in this registration statement of our report dated January 29, 1996 
(except with respect to the matter discussed in Note 10, as to which the date
is February 10, 1996) on the balance sheet of Dynamic Matrix Control
Corporation as of December 31, 1995 and the related statements of income,
stockholders' equity and cash flows for the year then ended, appearing in
Amendment No. 2 on Form 8-K/A to the Current Report on Form 8-K dated January
5, 1996 of Aspen Technology, Inc., (ii) the incorporation by reference in this
registration statement of our report dated March 8, 1996 on the consolidated
balance sheets of Setpoint, Inc. and subsidiaries as of December 31, 1995 and
1994, and the related consolidated statements of operations, stockholders'
equity and cash flows for the years then ended, appearing in Amendment No. 3 on
Form 8-K/A to such Current Report on Form 8-K dated January 5, 1996 of Aspen
Technology, Inc., (iii) the incorporation by reference in this registration
statement of our reports dated July 28, 1995 included in Aspen Technology,
Inc.'s Form 10-K for the year ended June
 30, 1995 and (iv) all references to
our Firm included in this registration statement.



                                                  /s/ Arthur Andersen LLP

                                                  ARTHUR ANDERSEN LLP

Boston, Massachusetts
September 9, 1996