<PAGE>
                                                                     EXHIBIT 4.2



                             ASPEN TECHNOLOGY, INC.


                           CERTIFICATE OF DESIGNATIONS
                                       OF
                             SERIES B-1 CONVERTIBLE
                                 PREFERRED STOCK
                                       AND
                             SERIES B-2 CONVERTIBLE
                                 PREFERRED STOCK


                (Pursuant to Section 151 of the Delaware General
                                Corporation Law)


            Aspen Technology, Inc., a Delaware corporation (the "Corporation"),
in accordance with the provisions of Section 103 of the Delaware General
Corporation Law (the "DGCL") does hereby certify that, in accordance with
Section 141(c) of the DGCL, the following resolution was duly adopted by the
Board of Directors of the Corporation as of February 4, 2002:

            RESOLVED, that two series of Preferred Stock, Series B-1 Convertible
Preferred Stock, par value $0.10 per share and Series B-2 Convertible Preferred
Stock, par value $0.10 per share, of the Corporation are hereby created and the
designation, number of shares, powers, preferences, rights, qualifications,
limitations and restrictions thereof (in addition to any provisions set forth in
the Certificate of Incorporation of the Corporation which are applicable to the
Preferred Stock of all classes and series) are as follows:

                     SERIES B-1 CONVERTIBLE PREFERRED STOCK
                                       AND
                     SERIES B-2 CONVERTIBLE PREFERRED STOCK

      1. Designation, Amount, Par Value and Stated Value. The following two (2)
series of preferred stock shall be designated as (i) the Corporation's Series
B-1 Convertible Preferred Stock (the "SERIES B-1 PREFERRED STOCK"), and the
number of shares so designated shall be 30,000 and (ii) the Corporation's Series
B-2 Convertible Preferred Stock (the "SERIES B-2 PREFERRED STOCK"), and the
number of shares so designated shall be 20,000. The Series B-1 Preferred Stock
and Series B-2 Preferred Stock are sometimes collectively referred to as the
"SERIES B PREFERRED STOCK." Each share of Series B Preferred Stock shall have a
par value of $0.10 per share and a stated value equal to $1,000 plus any amount
added to the Stated Value
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pursuant to Section 3(c) hereof or Section 2(c) of the Registration Rights
Agreement (the "STATED VALUE").

      2.          Definitions.  In addition to the terms defined elsewhere in
this Certificate of Designations, (a) the terms set forth in Exhibit A hereto
have the meanings indicated therein, and (b) the following terms have the
meanings indicated:

            "CONVERSION PRICE" means the Initial Conversion Price as of the
      applicable Original Issue Date, as adjusted pursuant to Section 15 below.

            "EQUITY CONDITIONS" means, with respect to a specified issuance of
      Common Stock, that each of the following conditions is satisfied: (i) the
      number of authorized but unissued and otherwise unreserved shares of
      Common Stock is sufficient for such issuance; (ii) such shares of Common
      Stock are registered for resale by the Holders and may be sold by the
      Holders pursuant to an effective Underlying Shares Registration Statement,
      all such shares may be sold without volume restrictions pursuant to Rule
      144(k) under the Securities Act or all Underlying Shares owned by each
      Holder may be sold without volume restrictions pursuant to Rule 144 under
      the Securities Act; (iii) the Common Stock is listed or quoted (and is not
      suspended from trading) on an Eligible Market and such shares of Common
      Stock are approved for listing upon issuance; (iv) such issuance would be
      permitted in full without violating Section 16 hereof or the rules or
      regulations of any Trading Market; (v) no Bankruptcy Event has occurred;
      (vi) the Corporation is not in default with respect to any material
      obligation hereunder or under any other Transaction Document; and (vii)
      none of the following events have occurred and are continuing (A) an event
      constituting a Triggering Event or (B) an event that with the passage of
      time and without being cured would constitute a Triggering Event other
      than a pending, proposed or intended Change of Control.

            "HOLDER" means any holder of Series B Preferred Stock.

            "INITIAL CONVERSION PRICE" means (i) in the case of Series B-1
      Preferred Stock, $19.9703, and (ii) in the case of Series B-2 Preferred
      Stock, the greater of (x) the lesser of (a) 117.5% of the average of the
      daily Volume Weighted Average Prices over the twenty (20) consecutive
      Trading Day period ending on February 27, 2002 (including such date) or
      (b) 112.5% of the average of the daily Volume Weighted Average Prices over
      the three (3) consecutive Trading Day period ending on February 27, 2002
      (including such date), or (y) $15.00 (as adjusted for any stock splits,
      stock dividends, stock combinations or


                                       2
<PAGE>
      similar events occurring after the Original Issue Date of the Series B-1
      Preferred Stock and prior to the Original Issue Date of the Series B-2
      Preferred Stock).

            "INITIAL PURCHASE PRICE" means (i) in the case of Series B-1
      Preferred Stock, $17.75, and (ii) in the case of Series B-2 Preferred
      Stock, the greater of (x) the lesser of (a) the average of the daily
      Volume Weighted Average Prices over the twenty (20) consecutive Trading
      Day period ending on February 27, 2002 (including such date) or (b) the
      average of the daily Volume Weighted Average Prices over the three (3)
      consecutive Trading Day period ending on February 27, 2002 (including such
      date), or (y) $15.00 (as adjusted for any stock splits, stock dividends,
      stock combinations or similar events occurring after the Original Issue
      Date of the Series B-1 Preferred Stock and prior to the Original Issue
      Date of the Series B-2 Preferred Stock).

            "JUNIOR SECURITIES" means the Common Stock and all other equity or
      equity equivalent securities of the Corporation.

            "ORIGINAL ISSUE DATE" means the date of the first issuance of any
      shares of the Series B-1 Preferred Stock or Series B-2 Preferred Stock, as
      applicable, regardless of the number of transfers of any particular shares
      of such Series B Preferred Stock and regardless of the number of
      certificates that may be issued to evidence such Series B Preferred Stock.

            "PURCHASE AGREEMENT" means the Securities Purchase Agreement, dated
      February 6, 2002, among the Corporation and the original purchasers of the
      Series B Preferred Stock.

      3.          Dividends.

            (a) Holders shall be entitled to receive, out of funds legally
available therefor, and the Corporation shall pay, cumulative dividends on the
Series B Preferred Stock at the rate per share (as a percentage of the Stated
Value per share) of 4% per annum, payable quarterly in arrears commencing on
June 30, 2002 and thereafter on each March 31, June 30, September 30 and
December 31, except if such date is not a Trading Day, in which case such
dividend shall be payable on the next succeeding Trading Day (each, a "DIVIDEND
PAYMENT DATE"). Dividends on the Series B Preferred Stock shall be calculated on
the basis of a 365-day year, shall accrue daily commencing on the Original Issue
Date for the applicable series of Series B Preferred Stock, and shall be deemed
to accrue from such date whether or not earned or declared and whether or not
there are profits, surplus or other funds of the Corporation legally available
for the payment of dividends.

            (b) Subject to the conditions and limitations set forth below, the
Corporation may pay required dividends (i) in cash or (ii) in Common Stock. The
Corporation must deliver written notice (the "DIVIDEND NOTICE") to the Holders
indicating the manner in which it intends to pay dividends at least ten Trading
Days prior to each Dividend Payment Date, but the Corporation may indicate in
any such notice that the election contained therein shall continue for
subsequent Dividend Payment Dates until revised. Failure to timely provide such
written notice shall be deemed an election by the Corporation to pay the
dividend in Common Stock, unless payment of dividends in such manner is not
permitted at the time of a dividend, in which case such dividend shall be
payable in cash. All dividends payable in respect of the Series B Preferred
Stock on any Dividend Payment Date must be paid in the same manner.

            (c) Notwithstanding the foregoing, the Corporation may not pay
dividends by issuing Common Stock unless, at such time, the Equity Conditions
are satisfied with respect to such Common Stock dividend shares and all of the
Underlying Shares then issuable upon conversion in full of all outstanding
Series B Preferred Stock. If the Corporation is required to pay dividends in
cash on any Dividend Payment Date and does not timely make such payment, any
Holder may (but shall not be required to) treat such cash amount as if it had
been added to


                                       3
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the Stated Value as of such Dividend Payment Date. If the Corporation may not
legally pay dividends on any Dividend Payment Date, such amount shall be added
to the Stated Value as of such Dividend Payment Date.

            (d) So long as any Series B Preferred Stock is outstanding, (i)
neither the Corporation nor any Subsidiary shall, directly or indirectly,
redeem, purchase or otherwise acquire any Junior Securities or set aside any
monies for such a redemption, purchase or other acquisition in excess of
$10,000,000 per calendar year, provided that the Corporation shall be entitled
to carry forward any amount not used in any calendar year to subsequent calendar
years, and (ii) the Corporation shall not pay or declare any dividend or make
any distribution on any Junior Securities, except pro rata stock dividends on
the Common Stock payable in additional shares of Common Stock and dividends due
and paid in the ordinary course on preferred stock of the Corporation, in each
case only at such times as the Corporation is in compliance with its payment and
other obligations hereunder.

            (e) In the event that the Corporation elects to pay dividends in
shares of Common Stock, the number of shares of Common Stock to be issued to
each Holder as such dividend shall be (i) determined by dividing the total
dividend then payable to such Holder by the Dividend Market Price (as defined
below) as of the applicable Dividend Payment Date, and rounding up to the
nearest whole share, and (ii) paid to such Holder in accordance with Section
3(f) below. The term "DIVIDEND MARKET PRICE" shall mean the average of the
Volume Weighted Average Prices of Common Stock for the five (5) consecutive
Trading Days prior to the applicable Dividend Payment Date (not including such
date).

            (f) In the event that any dividends are paid in Common Stock the
Corporation shall, on or before the third (3rd) Trading Day following the
payment date of such dividend, (i) issue and deliver to such Holder a
certificate, registered in the name of the Holder or its designee, for the
number of shares of Common Stock to which the Holder shall be entitled or (ii)
if and when the applicable shares of Common Stock may be held in a balance
account with The Depository Trust Corporation through its Deposit Withdrawal
Agent Commission System and after the Holder has notified the Corporation that
this clause (ii) shall apply, credit the number of shares of Common Stock to
which the Holder shall be entitled to the Holder's or its designee's balance
account with The Depository Trust Corporation through its Deposit Withdrawal
Agent Commission System.

      4. Registration of Series B Preferred Stock. The Corporation shall
register shares of the Series B Preferred Stock, upon records to be maintained
by the Corporation for that purpose (the "SERIES B PREFERRED STOCK REGISTER"),
in the name of the record Holders thereof from time to time. The Corporation may
deem and treat the registered Holder of shares of Series B Preferred Stock as
the absolute owner thereof for the purpose of any conversion hereof or any
distribution to such Holder, and for all other purposes, absent actual notice to
the contrary.

      5. Registration of Transfers. The Corporation shall register the transfer
of any shares of Series B Preferred Stock in the Series B Preferred Stock
Register, upon surrender of certificates evidencing such Shares to the
Corporation at its address specified herein. Upon any such registration or
transfer, a new certificate evidencing the shares of Series B Preferred Stock


                                       4
<PAGE>
so transferred shall be issued to the transferee and a new certificate
evidencing the remaining portion of the shares not so transferred, if any, shall
be issued to the transferring Holder.

      6.          Liquidation.

            (a) In the event of any liquidation, dissolution or winding up of
the Corporation, either voluntary or involuntary (a "LIQUIDATION EVENT"), the
Holders of Series B Preferred Stock shall be entitled to receive, prior and in
preference to any distribution of any of the assets or surplus funds of the
Corporation to the holders of Junior Securities by reason of their ownership
thereof, an amount per share in cash equal to the Stated Value for each share of
Series B Preferred Stock then held by them (as adjusted for any stock splits,
stock dividends, stock combinations and similar transactions with respect to the
Series B Preferred Stock), plus all accrued but unpaid dividends on such Series
B Preferred Stock as of the date of such event (the "SERIES B STOCK LIQUIDATION
Preference"). If, upon the occurrence of a Liquidation Event, the assets and
funds thus distributed among the holders of the Series B Preferred Stock shall
be insufficient to permit the payment to such Holders of the full Series B Stock
Liquidation Preference, then the entire assets and funds of the Corporation
legally available for distribution shall be distributed ratably among the
Holders of the Series B Preferred Stock in proportion to the aggregate Series B
Stock Liquidation Preference that would otherwise be payable to each of such
Holders.

            (b) In the event of a Liquidation Event, following completion of the
distributions required by the first sentence of paragraph (a) of this Section 6,
if assets or surplus funds remain in the Corporation, the holders of the Common
Stock shall share ratably in all remaining assets of the Corporation, based on
the number of shares of Common Stock then outstanding.

            (c) The Corporation shall mail written notice of any Liquidation
Event to each record Holder not less than 20 Trading Days prior to the payment
date or effective date thereof.

      7.          Conversion.

            (a) Conversion at Option of Holder. At the option of any Holder, any
Series B Preferred Stock held by such Holder may be converted into Common Stock
based on the applicable Conversion Price then in effect for such series of
Series B Preferred Stock. A Holder may convert Series B Preferred Stock into
Common Stock pursuant to this paragraph at any time and from time to time after
the applicable Original Issue Date, by delivering to the Corporation a
Conversion Notice, in the form attached hereto as Exhibit B, appropriately
completed and duly signed, and the date any such Conversion Notice is delivered
to the Corporation (as determined in accordance with the notice provisions
hereof) is a "Conversion Date."

            (b) Conversion at Option of Corporation. If, at any time after the
Effective Date, the Closing Price on each of twenty (20) consecutive Trading
Days (a "QUALIFYING PERIOD") exceeds 135% of the applicable Conversion Price for
a series of Series B Preferred Stock (each, a "THRESHOLD PRICE"), the
Corporation may require the Holders to convert the


                                       5
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shares of such series into Common Stock based on the applicable Conversion
Price. The Corporation may require a conversion pursuant to this paragraph by
delivering irrevocable written notice of such election to the Holders, and the
fifth Trading Day after the date any such notice is delivered to the Holders (as
determined in accordance with the notice provisions hereof) will be the
"CONVERSION DATE" for such required conversion. Notwithstanding the foregoing,
(i) if the Corporation has publicly announced a pending, proposed or intended
Change of Control and the Qualifying Period includes any Trading Days on or
after the date of such public announcement, then to the extent that a Holder has
not had the ability to sell all or a portion of the Underlying Shares pursuant
to Rule 144 under the Securities Act or an effective Underlying Share
Registration Statement for at least 20 Trading Days after the date of the public
announcement of such Change of Control, the Conversion Date with respect to
those shares of Series B Preferred Stock that are convertible into the portion
of the Underlying Shares that are not so saleable shall be deferred until the
date on which such Underlying Shares shall have been so saleable for a period of
20 Trading Days from the date of such public announcement (and if no such period
of 20 Trading Days occurs prior to the Change of Control with respect to any
such Underlying Shares then the notice of conversion applicable to those shares
of Series B Preferred Stock convertible into such Underlying Shares shall be
void) and (ii) the Corporation may not require any conversion under this
paragraph (and any notice thereof will be void), unless from the beginning of
such period of 20 consecutive Trading Days through the Conversion Date, (A) the
Equity Conditions are satisfied with respect to all of the Underlying Shares
then issuable upon conversion in full of all outstanding Series B Preferred
Stock, and (B) the Closing Price equals or exceeds the applicable Threshold
Price.

      8.          Mechanics of Conversion.

            (a) The number of Underlying Shares issuable upon any conversion of
shares of either series of Series B Preferred Stock hereunder shall equal (i)
the Stated Value of such share of Series B Preferred Stock to be converted,
divided by the applicable Conversion Price on the Conversion Date, plus (ii) the
amount of any accrued but unpaid dividends on such share of Series B Preferred
Stock through the Conversion Date, divided by the applicable Conversion Price on
the Conversion Date.

            (b) Upon conversion of any Series B Preferred Stock, the Corporation
shall promptly (but in no event later than three Trading Days after the
Conversion Date) issue or cause to be issued and cause to be delivered to or
upon the written order of the Holder and in such name or names as the Holder may
designate a certificate for the Underlying Shares issuable upon such conversion,
free of restrictive legends unless such Underlying Shares are not then freely
transferable without volume restrictions pursuant to Rule 144(k) under the
Securities Act. The Holder, or any Person so designated by the Holder to receive
Underlying Shares, shall be deemed to have become holder of record of such
Underlying Shares as of the Conversion Date. If and when such Underlying Shares
may be freely transferred pursuant to Rule 144 under the Securities Act or
pursuant to an effective Underlying Shares Registration Statement, the
Corporation shall use its best efforts to deliver Underlying Shares hereunder
electronically through the Depository Trust Corporation or another established
clearing corporation performing similar functions, and shall issue such
Underlying Shares in the same manner as dividend payment shares are issued
pursuant to Section 3(f) above.


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            (c) A Holder shall not be required to deliver the original
certificate(s) evidencing the Series B Preferred Stock being converted in order
to effect a conversion of such Series B Preferred Stock. Execution and delivery
of the Conversion Notice shall have the same effect as cancellation of the
original certificate(s) and issuance of a new certificate evidencing the
remaining shares of Series B Preferred Stock. Upon surrender of a certificate
following one or more partial conversions, the Corporation shall promptly
deliver to the Holder a new certificate representing the remaining shares of
Series B Preferred Stock.

            (d) The Corporation's obligations to issue and deliver Underlying
Shares upon conversion of Series B Preferred Stock in accordance with the terms
hereof are absolute and unconditional, irrespective of any action or inaction by
any Holder to enforce the same, any waiver or consent with respect to any
provision hereof, the recovery of any judgment against any Person or any action
to enforce the same, or any setoff, counterclaim, recoupment, limitation or
termination, or any breach or alleged breach by any Holder or any other Person
of any obligation to the Corporation or any violation or alleged violation of
law by any Holder or any other Person, and irrespective of any other
circumstance which might otherwise limit such obligation of the Corporation to
any Holder in connection with the issuance of such Underlying Shares.


      9.          Redemption Rights.

            (a)         Holders Redemption Rights.

                        (i) Subject to the provisions of Section 9(a)(iii)
            below, if, at any time on or after the eighteen (18) month
            anniversary of the applicable Original Issue Date of a Series B
            Preferred Stock, the average of the Closing Prices for twenty (20)
            consecutive Trading Days immediately preceding such eighteen (18)
            month anniversary or any date thereafter is below the applicable
            Conversion Price of such series of Series B Preferred Stock, the
            Holder of such Series B Preferred Stock, upon 15 Trading Days
            advance notice (the "REDEMPTION NOTICE") to the Corporation, shall
            have the right to request the Corporation to redeem that number of
            shares of Series B Preferred Stock held by such Holders as is set
            forth in the Redemption Notice at a per share price (the "REDEMPTION
            PRICE") equal to the Stated Value of such shares of Series B
            Preferred Stock to be redeemed plus all accrued but unpaid dividends
            thereon to the date of payment.

                        (ii) Notwithstanding anything to the contrary in Section
            9(a)(i), the Holders of the Series B Preferred Stock (x) may not
            deliver a Redemption Notice with respect to a particular series of
            Series B Preferred Stock until after the date that is eighteen (18)
            months after the Original Issue Date of such series of Series B
            Preferred Stock, (y) may not deliver a Redemption Notice covering in
            aggregate more than $15,000,000 of Stated Value, with respect to the
            Series B-1 Preferred Stock, and $10,000,000 of Stated Value, with
            respect to the Series B-2 Preferred Stock, until after the date that
            is twenty - four (24) months after the Original Issue Date of such
            series of Series B Preferred Stock, and (z) may deliver a Redemption
            Notice with respect to a particular series of Series B Preferred


                                       7
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            Stock after the date that is twenty-four (24) months after the
            Original Issue Date of such series of Series B Preferred Stock,
            irrespective of whether the average of the Closing Prices for the
            twenty (20) consecutive Trading Days is below the applicable
            Conversion Price of such series of Series B Preferred Stock and
            without limit as to Stated Value.

                        (iii) Within three (3) Trading Days of receipt of a
            Redemption Notice, the Corporation will deliver written notice to
            each Holder of the applicable series of Series B Preferred Stock
            (the "CORPORATION NOTICE"), confirming pursuant to the Redemption
            Notice the aggregate amount of such Series B Preferred Stock being
            redeemed, the Redemption Date and the applicable Redemption Prices.
            Notwithstanding the aggregate shares set forth in the Redemption
            Notice, each Holder of such series of Series B Preferred Stock shall
            have the right to elect to have all or any number of shares of the
            applicable series of Series B Preferred Stock held by such Holder
            redeemed on the Redemption Date at the applicable Redemption Price
            by notifying the Corporation within five (5) Trading Days of receipt
            of the Corporation Notice of its election to do so, and specifying
            the number of shares as to which such election is made. In the event
            that the aggregate number of shares of Series B Preferred Stock to
            be redeemed on such Redemption Date exceeds the aggregate
            limitations set forth in Section 9(a)(ii), the number of shares to
            be redeemed from each Holder shall be reduced pro rata based upon
            the aggregate number of shares of the applicable series of Series B
            Preferred Stock held by each Holder requesting redemption.

                        (iv) The Redemption Notice will specify the effective
            date of the redemption, which must be a Trading Day at least 15
            Trading Days after the date such notice is delivered (the
            "REDEMPTION DATE"), and the entire Redemption Price may be paid at
            the Corporation's option in cash or in Common Stock. The Corporation
            must deliver written notice to the Holders indicating the manner in
            which it intends to pay the Redemption Price at least three (3)
            Trading Days after receipt of the Redemption Notice. Failure to
            timely provide such written notice shall be deemed an election by
            the Corporation to make the payment in Common Stock. Notwithstanding
            the foregoing, the Corporation may not pay the Redemption Price by
            issuing Common Stock unless, at such time, the Equity Conditions are
            satisfied with respect to such Common Stock.

                        (v) Upon receipt of payment of the Redemption Price,
            each Holder will deliver the original certificate(s) evidencing the
            Series B Preferred Stock so redeemed to the Corporation, unless such
            Holder is awaiting receipt of a new certificate evidencing such
            shares from the Corporation pursuant to another provision hereof. At
            any time on or prior to the Corporation Redemption Date, the Holders
            may convert any or all of the shares of Series B Preferred Stock,
            and the Corporation shall honor any such conversions in accordance
            with the terms hereof.

                        (vi) In the event that the Corporation elects to pay the
            Redemption Price in shares of Common


                                       8
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            Stock, the number of shares of Common Stock to be issued to each
            Holder as payment of the Redemption Price shall be determined by
            dividing the total Redemption Price then payable to such Holder by
            the Redemption Market Price (as defined below) as of the applicable
            Redemption Date, and rounding up to the nearest whole share. Such
            shares shall be issued to such Holder in the same manner as dividend
            payment shares are issued pursuant to Section 3(f) above. The term
            "REDEMPTION MARKET PRICE" shall mean the average of the Volume
            Weighted Average Prices of Common Stock for the ten (10) consecutive
            Trading Days prior to the applicable Redemption Date (not including
            such date).

            (b) Mandatory Redemption. On the seven year anniversary of the
Original Issue Date of the Series B-1 Preferred Stock (the "MANDATORY REDEMPTION
DATE"), the Corporation shall redeem all of the then outstanding Series B
Preferred Stock at a price equal to 100% of the Stated Value of such shares of
Series B Preferred Stock plus all accrued but unpaid dividends thereon to the
date of payment in cash or Common Stock (or a combination thereof) at the
election of the Corporation. The Corporation must deliver written notice to the
Holders indicating the manner in which it intends to pay the Redemption Price at
least twenty (20) Trading Days prior to the Mandatory Redemption Date. Failure
to timely provide such written notice shall be deemed an election by the
Corporation to make the payment in Common Stock. Notwithstanding the foregoing,
the Corporation may not pay the Redemption Price by issuing Common Stock except
to the extent the Equity Conditions are satisfied with respect to such Common
Stock. Upon receipt of payment of the Redemption Price, each Holder will deliver
the original certificate(s) evidencing the Series B Preferred Stock so redeemed
to the Corporation, unless such Holder is awaiting receipt of a new certificate
evidencing such shares from the Corporation pursuant to another provision
hereof. At any time on or prior to the Mandatory Redemption Date, the Holders
may convert any or all of the shares of Series B Preferred Stock, and the
Corporation shall honor any such conversions in accordance with the terms
hereof.

      10. Triggering Events. At any time or times following the occurrence of a
Triggering Event (other than a Change of Control), each Holder shall have the
option to elect, by notice to the Corporation (an "EVENT NOTICE"), to require
the Corporation to repurchase all or any portion of (i) the Series B Preferred
Stock then held by such Holder, at a price per share equal to the greater of (A)
115% of the Stated Value plus all accrued but unpaid dividends thereon through
the date of payment, or (B) the Event Equity Value of the Underlying Shares
issuable upon conversion of such Series B Preferred Stock (including such
accrued but unpaid dividends thereon), and (ii) any Underlying Shares issued to
such Holder upon conversion of Series B Preferred Stock, at a price per share
equal to the Event Equity Value of such Underlying Shares. The aggregate amount
payable pursuant to the preceding sentence is referred to as the "EVENT PRICE."
The Corporation shall pay the aggregate Event Price to each Holder no later than
the third Trading Day following the date of delivery of the Event Notice, and
upon receipt thereof such Holder shall deliver original certificates evidencing
the shares of Series B Preferred Stock and Underlying Shares so repurchased to
the Corporation (to the extent such certificates have been delivered to the
Holder).

      11. Voting Rights. Except as otherwise provided herein or as required by
applicable law, the Holders of the Series B Preferred Stock shall be entitled to
vote on all matters on which holders of Common Stock are entitled to vote,
including, without limitation, the election of


                                       9
<PAGE>
directors. For such purposes, each Holder shall be entitled to a number of votes
in respect of the shares of Series B Preferred Stock owned by it equal to the
number of shares of Common Stock into which such shares of Series B Preferred
Stock are convertible as of the record date for the determination of
stockholders entitled to vote on such matter, or if no record date is
established, at the date such vote is taken or any written consent of
stockholders is solicited. Except as otherwise provided herein, in any relevant
agreement or as required by applicable law, the holders of the Series B
Preferred Stock and Common Stock, respectively, shall vote together as a single
class on all matters submitted to a vote or consent of stockholders; provided
that so long as any shares of Series B Preferred Stock are outstanding, the
Corporation shall not, without the affirmative vote of the Holders of a majority
of the shares of Series B Preferred Stock then outstanding, (a) alter or change
adversely the powers, preferences or rights given to the Series B Preferred
Stock or alter or amend this Certificate of Designations (whether by merger,
reorganization, consolidation or otherwise), (b) authorize or create any class
of stock ranking as to dividends or distribution of assets upon a Liquidation
Event or Change of Control senior to the Series B Preferred Stock, (c) amend its
certificate of incorporation or bylaws so as to affect adversely any rights of
the Holders (whether by merger, reorganization, consolidation or otherwise), (d)
increase the authorized number of shares of Series B Preferred Stock, or (e)
enter into any agreement with respect to the foregoing.

      12. Charges, Taxes and Expenses. Issuance of certificates for shares of
Series B Preferred Stock and for Underlying Shares issued on conversion of (or
otherwise in respect of) the Series B Preferred Stock shall be made without
charge to the Holders for any issue or transfer tax, withholding tax, transfer
agent fee or other incidental tax or expense in respect of the issuance of such
certificates, all of which taxes and expenses shall be paid by the Corporation;
provided, however, that the Corporation shall not be required to pay any tax
that may be payable in respect of any transfer involved in the registration of
any certificates for Common Stock or Series B Preferred Stock in a name other
than that of the Holder. The Holder shall be responsible for all other tax
liability that may arise as a result of holding or transferring the Series B
Preferred Stock or receiving Underlying Shares in respect of the Series B
Preferred Stock.

      13. Replacement Certificates. If any certificate evidencing Series B
Preferred Stock or Underlying Shares is mutilated, lost, stolen or destroyed,
the Corporation shall issue or cause to be issued in exchange and substitution
for and upon cancellation hereof, or in lieu of and substitution for such
certificate, a new certificate, but only upon receipt of evidence reasonably
satisfactory to the Corporation of such loss, theft or destruction and customary
and reasonable indemnity, if requested. Applicants for a new certificate under
such circumstances shall also comply with such other reasonable regulations and
procedures and pay such other reasonable third-party costs as the Corporation
may prescribe.

      14. Reservation of Underlying Shares. The Corporation covenants that it
shall at all times reserve and keep available out of the aggregate of its
authorized but unissued and otherwise unreserved Common Stock, solely for the
purpose of enabling it to issue the Underlying Shares as required hereunder (i)
a sufficient number of authorized but unissued and otherwise unreserved shares
of Common Stock available to issue Underlying Shares upon any conversion of
Shares or, if the number of shares so reserved is insufficient to make available
a sufficient number of authorized but unissued and otherwise unreserved shares
of Common Stock


                                       10
<PAGE>
for such issuance within 60 days after the occurrence of such deficiency, and
(ii) at least 5,825,000 authorized but unissued and otherwise unreserved shares
of Common Stock (as adjusted for any stock splits, stock combinations or similar
events) less any shares of Common Stock issued upon conversion of the Shares, as
dividends on the Shares, upon exercise of the Warrants or upon a redemption of
the Shares. The Corporation covenants that all Underlying Shares so issuable and
deliverable shall, upon issuance in accordance with the terms hereof, be duly
and validly authorized, issued and fully paid and nonassessable.

      15.         Certain Adjustments.  The Conversion Price is subject to
adjustment from time to time as set forth in this Section 15.

            (a) Stock Dividends and Splits. If the Corporation, at any time
while Series B Preferred Stock is outstanding, (i) pays a stock dividend on its
Common Stock or otherwise makes a distribution on any class of capital stock
that is payable in shares of Common Stock (other than regular dividends on the
Series B Preferred Stock), (ii) subdivides outstanding shares of Common Stock
into a larger number of shares, or (iii) combines outstanding shares of Common
Stock into a smaller number of shares, then in each such case the applicable
Conversion Price for each series of Series B Preferred Stock shall be multiplied
by a fraction of which the numerator shall be the number of shares of Common
Stock outstanding immediately before such event and of which the denominator
shall be the number of shares of Common Stock outstanding immediately after such
event. Any adjustment made pursuant to clause (i) of this paragraph shall become
effective immediately after the record date for the determination of
stockholders entitled to receive such dividend or distribution, and any
adjustment pursuant to clause (ii) or (iii) of this paragraph shall become
effective immediately after the effective date of such subdivision or
combination.

            (b) Pro Rata Distributions. If the Corporation, at any time while
Series B Preferred Stock is outstanding, distributes to all holders of Common
Stock (i) evidences of its indebtedness, (ii) any security (other than a
distribution of Common Stock covered by the preceding paragraph), (iii) rights
or warrants to subscribe for or purchase any security, or (iv) any other asset
other than cash paid as a dividend (in each case, "DISTRIBUTED PROPERTY"), then,
at the request of any Holder delivered before the 90th day after the record date
fixed for determination of stockholders entitled to receive such distribution,
the Corporation will deliver to such Holder, within five Trading Days after such
request (or, if later, on the effective date of such distribution), the
Distributed Property that such Holder would have been entitled to receive in
respect of the Underlying Shares for which such Holder's Series B Preferred
Stock could have been converted immediately prior to such record date. If such
Distributed Property is not delivered to a Holder pursuant to the preceding
sentence, then upon any conversion of Series B Preferred Stock that occurs after
such record date, such Holder shall be entitled to receive, in addition to the
Underlying Shares otherwise issuable upon such conversion, the Distributed
Property that such Holder would have been entitled to receive in respect of such
number of Underlying Shares had the Holder been the record holder of such
Underlying Shares immediately prior to such record date.

            (c) Change of Control Transactions. If, at any time while Series B
Preferred Stock is outstanding, the Corporation proposes to enter into a
transaction that would constitute a Change of Control, the Corporation shall
mail written notice of the proposed Change of Control


                                       11
<PAGE>
transaction to each record Holder not less than 20 Trading Days prior to the
effective date thereof. Each Holder shall have the right to receive on the date
of the consummation of such Change of Control, at its option, either (i) for
each Underlying Share that would have been issuable upon such conversion of the
shares of Series B Preferred Stock upon the effective time of such Change of
Control, the same kind and amount of securities, cash or property as it would
have been entitled to receive upon the occurrence of such Change of Control if
it had been, immediately prior to such Change of Control, the holder of one
share of Common Stock or (ii) for each share of Series B Preferred Stock, cash
in an amount equal to 115% of the Stated Value plus all accrued but unpaid
dividends thereon through the date of payment. If holders of Common Stock are
given any choice as to the securities, cash or property to be received in a
Change of Control transaction, then each Holder shall be given the same choice
as to the consideration it receives pursuant to clause (i) above. Each Holder
shall make the election of which consideration it has elected to receive at
least three (3) Trading Days prior to the effective date of a Change of Control.
Failure of any Holder to timely provide written notice of its election shall be
deemed an election by such Holder to receive the consideration specified in
clause (ii) above.

            (d)         Subsequent Equity Sales.

                        (i) If, at any time while any shares of either series of
            Series B Preferred Stock are outstanding, the Corporation or any
            Subsidiary issues additional shares of Common Stock or rights,
            warrants, options or other securities or debt convertible,
            exercisable or exchangeable for shares of Common Stock or otherwise
            entitling any Person to acquire shares of Common Stock
            (collectively, "COMMON STOCK EQUIVALENTS") at an effective net price
            to the Corporation per share of Common Stock (the "EFFECTIVE PRICE")
            less than the lesser of (A) the Initial Purchase Price for a series
            of Series B Preferred Stock or (B) then-applicable Conversion Price
            for a series of Series B Preferred Stock, then the applicable
            Conversion Price for such series of Series B Preferred Stock shall
            be reduced to equal the Effective Price. For purposes of this
            paragraph, in connection with any issuance of any Common Stock
            Equivalents, (A) the maximum number of shares of Common Stock
            potentially issuable at any time upon conversion, exercise or
            exchange of such Common Stock Equivalents (the "DEEMED NUMBER")
            shall be deemed to be outstanding upon issuance of such Common Stock
            Equivalents, (B) the Effective Price applicable to such Common Stock
            shall equal the minimum dollar value of consideration payable to the
            Corporation to purchase such Common Stock Equivalents and to
            convert, exercise or exchange them into Common Stock (net of any
            discounts, fees, commissions and other expenses), divided by the
            Deemed Number, (C) no further adjustment shall be made to the
            Conversion Price upon the actual issuance of Common Stock upon
            conversion, exercise or exchange of such Common Stock Equivalents,
            and (D) upon the expiration or termination of any Common Stock
            Equivalent that does not result in the issuance of any Common Stock
            or additional Common Stock Equivalent, any adjustment that has been
            made under this paragraph (d) in respect of the issuance of such
            Common Stock Equivalent shall be readjusted as if such Common Stock
            Equivalent had not been issued (but shall in no event affect
            previously converted stock).


                                       12
<PAGE>
                        (ii) If, at any time while Series B Preferred Stock is
            outstanding, the Corporation or any Subsidiary issues Common Stock
            Equivalents with an Effective Price or a number of underlying shares
            that floats or resets or otherwise varies or is subject to
            adjustment based (directly or indirectly) on market prices of the
            Common Stock (a "FLOATING PRICE SECURITY"), then for purposes of
            applying the preceding paragraph in connection with any subsequent
            conversion, the Effective Price will be determined separately on
            each Conversion Date and will be deemed to equal the lowest
            Effective Price at which any holder of such Floating Price Security
            is entitled to acquire Common Stock on such Conversion Date
            (regardless of whether any such holder actually acquires any shares
            on such date).

                        (iii) Notwithstanding the foregoing, no adjustment will
            be made under this paragraph (d) in respect of the issuance of
            Excluded Stock.

            (e) Calculations. All calculations under this Section 15 shall be
made to the nearest cent or the nearest 1/100th of a share, as applicable. The
number of shares of Common Stock outstanding at any given time shall not include
shares owned or held by or for the account of the Corporation, and the
disposition of any such shares shall be considered an issue or sale of Common
Stock.

            (f) Notice of Adjustments. Upon the occurrence of each adjustment
pursuant to this Section 15, the Corporation at its expense will promptly
compute such adjustment in accordance with the terms hereof and prepare a
certificate describing in reasonable detail such adjustment and the transactions
giving rise thereto, including all facts upon which such adjustment is based.
Upon written request, the Corporation will promptly deliver a copy of each such
certificate to each Holder and to the Corporation's Transfer Agent.

            (g) Notice of Corporate Events. If the Corporation (i) declares a
dividend or any other distribution of cash, securities or other property in
respect of its Common Stock, including without limitation any granting of rights
or warrants to subscribe for or purchase any capital stock of the Corporation or
any Subsidiary, (ii) authorizes or approves, enters into any agreement
contemplating or solicits stockholder approval for any Fundamental Transaction
or (iii) authorizes the voluntary dissolution, liquidation or winding up of the
affairs of the Corporation, then the Corporation shall deliver to each Holder a
notice describing the material terms and conditions of such transaction, at
least 20 calendar days prior to the applicable record or effective date on which
a Person would need to hold Common Stock in order to participate in or vote with
respect to such transaction, and the Corporation will take all steps reasonably
necessary in order to insure that each Holder is given the practical opportunity
to convert its Series B Preferred Stock prior to such time so as to participate
in or vote with respect to such transaction; provided, however, that the failure
to deliver such notice or any defect therein shall not affect the validity of
the corporate action required to be described in such notice.

      16.         Limitation on Conversion.

            (a) Notwithstanding anything to the contrary contained herein, the
number of shares of Common Stock that may be acquired by any Holder upon any
conversion of Series B


                                       13
<PAGE>
Preferred Stock (or otherwise in respect of the Series B Preferred Stock) shall
be limited to the extent necessary to insure that, following such conversion (or
other issuance), the total number of shares of Common Stock then beneficially
owned by such Holder and its Affiliates and any other Persons whose beneficial
ownership of Common Stock would be aggregated with the Holder's for purposes of
Section 13(d) of the Exchange Act, does not exceed 4.999% (the "MAXIMUM
PERCENTAGE") of the total number of issued and outstanding shares of Common
Stock (including for such purpose the shares of Common Stock issuable upon such
conversion). For such purposes, beneficial ownership shall be determined in
accordance with Section 13(d) of the Exchange Act and the rules and regulations
promulgated thereunder. Each delivery of a Conversion Notice by a Holder will
constitute a representation by such Holder that it has evaluated the limitation
set forth in this paragraph and determined that issuance of the full number of
Underlying Shares requested in such Conversion Notice is permitted under this
paragraph. By written notice to the Corporation, any Holder may waive the
provisions of this Section or increase or decrease the Maximum Percentage to any
other percentage specified in such notice, but (i) any such waiver or increase
will not be effective until the 61st day after such notice is delivered to the
Corporation, and (ii) any such waiver or increase or decrease will apply only to
such Holder and not to any other Holder and (iii) any such waiver or increase
shall not be effective to the extent such waiver or increase would cause the
Corporation to violate the Nasdaq Stockholder Approval Rule.

            (b) For purposes of this Section 16, in determining the number of
outstanding shares of Common Stock, a Holder may rely on the number of
outstanding shares of Common Stock as reflected in (1) the Corporation's most
recent Form 10-Q, Form 10-K or other public filing with the Commission, as the
case may be, (2) a more recent public announcement by the Corporation, or (3)
any other notice by the Corporation or its transfer agent setting forth the
number of shares of Common Stock outstanding. Upon the written request of any
Holder, the Corporation shall promptly, but in no even later than one (1)
Trading Day following the receipt of such notice, confirm in writing to any such
Holder the number of shares of Common Stock then outstanding.

      17. Fractional Shares. The Corporation shall not be required to issue or
cause to be issued fractional Underlying Shares on conversion of Series B
Preferred Stock. If any fraction of an Underlying Share would, except for the
provisions of this Section, be issuable upon conversion of Series B Preferred
Stock, the number of Underlying Shares to be issued will be rounded up to the
nearest whole share.

      18. Notices. Any and all notices or other communications or deliveries
hereunder (including without limitation any Conversion Notice) shall be in
writing and shall be deemed given and effective on the earliest of (i) the date
of transmission, if such notice or communication is delivered via facsimile at
the facsimile number specified in this Section prior to 5:30 p.m. (New York City
time) on a Trading Day, (ii) the next Trading Day after the date of
transmission, if such notice or communication is delivered via facsimile at the
facsimile number specified in this Section on a day that is not a Trading Day or
later than 5:30 p.m. (New York City time) on any Trading Day, (iii) the Trading
Day following the date of mailing, if sent by nationally recognized overnight
courier service, or (iv) upon actual receipt by the party to whom such notice is
required to be given. The addresses for such communications shall be: (i) if to
the Corporation, to 10 Canal Park, Cambridge, Massachusetts 02141, facsimile:
(617) 949-1722,


                                       14
<PAGE>
attention: Chief Executive Officer and General Counsel, or (ii) if to a Holder,
to the address or facsimile number appearing on the Corporation's stockholder
records or such other address or facsimile number as such Holder may provide to
the Corporation in accordance with this Section.

      19.         Miscellaneous.

            (a) The headings herein are for convenience only, do not constitute
a part of this Certificate of Designations and shall not be deemed to limit or
affect any of the provisions hereof.

            (b) Any of the rights of the Holders of Series B Preferred Stock set
forth herein may be waived by the affirmative vote of the holders of a majority
of the shares of Series B Preferred Stock then outstanding. No waiver of any
default with respect to any provision, condition or requirement of this
Certificate of Designations shall be deemed to be a continuing waiver in the
future or a waiver of any subsequent default or a waiver of any other provision,
condition or requirement hereof, nor shall any delay or omission of either party
to exercise any right hereunder in any manner impair the exercise of any such
right.


      IN WITNESS WHEREOF, Aspen Technology, Inc. has caused this Certificate of
Designations to be duly executed as of this 6th day of February, 2002.



                                    ASPEN TECHNOLOGY, INC.



                                         By: /s/ Lisa W. Zappala
                                             --------------------
                                             Name:  Lisa W. Zappala
                                             Title: Senior Vice President,
                                                    Finance and Chief Financial
                                                    Officer


                                       15
<PAGE>
                                                                       EXHIBIT A



                             ADDITIONAL DEFINITIONS


      "AFFILIATE" means any Person that, directly or indirectly through one or
more intermediaries, controls or is controlled by or is under common control
with a Person, as such terms are used in and construed under Rule 144. With
respect to a Purchaser, any investment fund or managed account that is managed
on a discretionary basis by the same investment manager as such Purchaser will
be deemed to be an Affiliate of such Purchaser.

      "BANKRUPTCY EVENT" means any of the following events: (a) the Corporation
or any Material Subsidiary commences a case or other proceeding under any
bankruptcy, reorganization, arrangement, adjustment of debt, relief of debtors,
dissolution, insolvency or liquidation or similar law of any jurisdiction
relating to the Corporation or any Material Subsidiary thereof; (b) there is
commenced against the Corporation or any Material Subsidiary any such case or
proceeding that is not dismissed within 60 days after commencement; (c) the
Corporation or any Material Subsidiary is adjudicated insolvent or bankrupt or
any order of relief or other order approving any such case or proceeding is
entered; (d) the Corporation or any Material Subsidiary suffers any appointment
of any custodian or the like for it or any substantial part of its property that
is not discharged or stayed within 60 days; (e) the Corporation or any Material
Subsidiary makes a general assignment for the benefit of creditors; (f) the
Corporation or any Material Subsidiary fails to pay, or states in writing that
it is unable to pay or is unable to pay, its debts generally as they become due;
or (g) the Corporation or any Subsidiary, by any act or failure to act,
expressly indicates its consent to, approval of or acquiescence in any of the
foregoing or takes any corporate or other action that effects any of the
foregoing.

      "CHANGE OF CONTROL" means the occurrence of any of the following in one or
a series of related transactions: (i) an acquisition after the date hereof by an
individual or legal entity or "group" (as described in Rule 13d-5(b)(1) under
the Exchange Act) of a majority of the voting rights or equity interests in the
Corporation; (ii) a replacement of more than one-half of the members of the
Corporation's Board of Directors that is not approved by those individuals who
are members of the Board of Directors on the date hereof (or other directors
previously approved by such individuals); (iii) a merger or consolidation of the
Corporation or a sale of all or substantially all of the assets of the
Corporation in one or a series of related transactions, unless following such
transaction or series of transactions, the holders of the Corporation's
securities prior to the first such transaction continue to hold, directly or
indirectly, at least a majority of the voting rights and equity interests in the
surviving entity or acquirer of such assets; (iv) a recapitalization,
reorganization or other transaction involving the Corporation that constitutes
or results in a transfer of a majority of the voting rights or equity interests
in the Corporation to Persons other than holders of the Corporation's voting
equity securities prior to such transaction; or (v) consummation of a "Rule
13e-3 transaction" as defined in Rule 13e-3 under the Exchange Act with respect
to the Corporation other than a Rule 13e-3 transaction in which no Purchaser's
interest in the Corporation has been adversely changed or diluted in any
material manner.


                                       16
<PAGE>
      "CLOSING PRICE" means, for any date, the price determined by the first of
the following clauses that applies: (a) if the Common Stock is then listed or
quoted on an Eligible Market or any other national securities exchange, the last
closing price per share of the Common Stock for such date (or the nearest
preceding date) on the primary Eligible Market or exchange on which the Common
Stock is then listed or quoted; (b) if prices for the Common Stock are then
quoted on the OTC Bulletin Board, the average of the highest closing bid price
and the lowest closing ask price per share of the Common Stock for such date (or
the nearest preceding date) so quoted; (c) if prices for the Common Stock are
then reported in the "Pink Sheets" published by the National Quotation Bureau
Incorporated (or a similar organization or agency succeeding to its functions of
reporting prices), the most recent bid price per share of the Common Stock so
reported; or (d) in all other cases, the fair market value of a share of Common
Stock as determined by an independent appraiser selected in good faith by a
majority-in-interest of the Purchasers and the Corporation.

      "COMMISSION" means the Securities and Exchange Commission.

      "COMMON STOCK" means the common stock of the Corporation, par value $0.10
per share.

      "EFFECTIVE DATE" means the date that an Underlying Shares Registration
Statement is declared effective by the Commission.

      "ELIGIBLE MARKET" means the New York Stock Exchange, the American Stock
Exchange, the Nasdaq National Market or the Nasdaq SmallCap Market.

      "EVENT EQUITY VALUE" means 115% of the average of the Closing Prices for
the five Trading Days preceding the date of delivery of the notice requiring
payment of the Event Equity Value, provided that if the Corporation does not
make such required payment (together with any other payments, expenses and
liquidated damages then due and payable under the Transaction Documents) when
due or, in the event the Corporation disputes in good faith the occurrence of
the Triggering Event pursuant to which such notice relates, does not instead
deposit such required payment (together with such other payments, expenses and
liquidated damages then due) in escrow with an independent third-party escrow
agent within five Trading Days of the date such required payment is due, then
the Event Equity Value shall be 115% of the greater of (a) the average of the
Closing Prices for the five Trading Days preceding the date of delivery of the
notice requiring payment of the Event Equity Value and (b) the average of the
Closing Prices for the five Trading Days preceding the date on which such
required payment (together with such other payments, expenses and liquidated
damages) is paid in full.

      "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended.

      "EXCLUDED STOCK" means any shares of Common Stock issued or issuable (A)
upon exercise, conversion or exchange of any Common Stock Equivalents described
in Schedule 3.1(g) to the Purchase Agreement (provided that such exercise or
conversion occurs in accordance with the terms thereof, without amendment or
modification, and that the applicable exercise or conversion price or ratio is
described in such schedule); (B) to officers, directors, employees or
consultants of the Corporation pursuant to a stock option plan, employee stock


                                       17
<PAGE>
purchase plan or other equity incentive plan approved by the Board of Directors
of the Corporation; (C) pursuant to as part of a bona fide firm commitment
underwritten public offering with a nationally recognized underwriter (including
any "at the market offering," as defined in Rule 415(a)(4) under the Securities
Act, only if such offering does not constitute an "equity line" and generates
aggregate gross proceeds of at least $50 million); (D) in connection with any
transaction with a strategic investor, vendor, lessor, customer, supplier,
marketing partner, developer or integrator or any similar arrangement, in each
case the primary purpose of which is not to raise equity capital; (E) in
connection with a transaction involving a merger or acquisition of an entity,
business or assets (not principally for the purpose of obtaining cash); or (F)
in connection with any other transaction for consideration other than cash up to
108,166 shares of Common Stock in the aggregate (as adjusted for stock splits,
stock combinations and similar events).

      "MATERIAL SUBSIDIARY" means any significant subsidiary, as defined in Rule
1-02(w) of Regulation S-X promulgated by the Commission, of the Corporation.

      "PERSON" means an individual or corporation, partnership, trust,
incorporated or unincorporated association, joint venture, limited liability
Corporation, joint stock Corporation, government (or an agency or subdivision
thereof) or other entity of any kind.

      "PURCHASER" has the meaning set forth in the Purchase Agreement.

      "REGISTRATION RIGHTS AGREEMENT" means the Registration Rights Agreement,
dated as of February 6, 2002 among the Corporation and the Purchasers.

      "REQUIRED EFFECTIVENESS DATE" means the date on which an Underlying Shares
Registration Statement is required to become effective pursuant to the
Registration Rights Agreement.

      "RULE 144" means Rule 144 promulgated by the Commission pursuant to the
Securities Act, as such Rule may be amended from time to time, or any similar
rule or regulation hereafter adopted by the Commission having substantially the
same effect as such Rule.

      "SECURITIES" means the Shares, the Warrants and the Underlying Shares.

      "SECURITIES ACT" means the Securities Act of 1933, as amended.

      "SHARES" means, collectively, the shares of Series B-1 Preferred Stock and
Series B-2 Preferred Stock.

      "SUBSIDIARY" means any subsidiary, as defined in Rule 1-02(x) of
Regulation S-X promulgated by the Commission, of the Corporation.

      "TRADING DAY" means (a) any day on which the Common Stock is traded on its
primary Trading Market, or (b) if the Common Stock is not then listed or quoted
on any national securities exchange, market or trading or quotation facility,
then a day on which trading occurs on the New York Stock Exchange (or any
successor thereto).


                                       18
<PAGE>
      "TRADING MARKET" means the Nasdaq National Market or any other Eligible
Market on which the Common Stock is then listed or quoted.

      "TRANSACTION DOCUMENTS" means the Purchase Agreement, the Registration
Rights Agreement, this Certificate of Designations and the Warrants.

      "TRIGGERING EVENT" means any of the following events: (a) immediately
prior to any Bankruptcy Event; (b) the Common Stock is not listed or quoted, or
is suspended from trading, on an Eligible Market for a period of five
consecutive Trading Days or ten aggregate Trading Days in any 365 day period;
(c) the Corporation fails for any reason to deliver a certificate evidencing any
Securities to a Purchaser within ten Trading Days after delivery of such
certificate is required pursuant to any Transaction Document or the exercise or
conversion rights of the Holders pursuant to the Transaction Documents are
otherwise suspended for any reason; (d) the Corporation fails to have available
both (i) a sufficient number of authorized but unissued and otherwise unreserved
shares of Common Stock available to issue Underlying Shares upon any exercise of
the Warrants or any conversion of Shares and does not make available a
sufficient number of authorized but unissued and otherwise unreserved shares of
Common Stock for such issuance within 60 days after the occurrence of such
deficiency and (ii) at least 5,825,000 authorized but unissued and otherwise
unreserved shares of Common Stock (as adjusted for any stock splits, stock
combinations or similar events), less reductions reasonably agreed to by the
Purchasers to reflect shares of Common Stock issued upon conversion of the
Shares (and, therefore, reduced aggregate dividend payments), as dividends on
the Shares, upon exercise of the Warrants or upon a redemption of the Shares;
(e) at any time after the Required Effectiveness Date, any Common Stock issuable
pursuant to the Transaction Documents is not listed on an Eligible Market; (f)
any other Event (as defined in the Registration Rights Agreement) occurs and
remains uncured for 60 days; (g) the Corporation fails to make any cash payment
required under the Transaction Documents and such failure is not cured within
five days after notice of such default is first given to the Corporation by a
Purchaser; (h) the Corporation defaults in the timely performance of any other
obligation under the Transaction Documents and such default continues uncured
for a period of 20 days after the date on which notice of such default is first
given to the Corporation by a Purchaser (it being understood that no prior
notice need be given in the case of a default that cannot reasonably be cured
within 20 days), or (i) any Change of Control event.

      "UNDERLYING SHARES" means the shares of Common Stock issuable upon
conversion of, or in redemption of, the Shares, as payment of dividends on the
Shares and upon exercise of the Warrants, and any securities issued in exchange
for, or upon conversion or in respect of, such shares.

      "UNDERLYING SHARES REGISTRATION STATEMENT" means a registration statement
meeting the requirements set forth in the Registration Rights Agreement and
covering the resale of the Underlying Shares by the Purchasers.

      "VOLUME WEIGHTED AVERAGE PRICE" means, with respect to a Trading Day, the
average of the daily volume weighted average trading price (the total dollar
amount traded on each day divided by trading volume for such day) of the Common
Stock for the regular Trading Day


                                       19
<PAGE>
session as reported at 4:15 (New York time) as reported by Bloomberg, LP
function key HP by using W to calculate the daily weighted average.

      "WARRANTS" means the Common Stock purchase warrants issued pursuant to the
Purchase Agreement.


                                       20
<PAGE>
                                                                       EXHIBIT B



                            FORM OF CONVERSION NOTICE

(To be executed by the registered Holder
in order to convert shares of Series B Preferred Stock)

The undersigned hereby elects to convert the number of shares of Series B
Convertible Preferred Stock indicated below into shares of common stock, par
value $0.10 per share (the "COMMON STOCK"), of Aspen Technology, Inc., a
Delaware corporation (the "CORPORATION"), according to the conditions hereof, as
of the date written below.


                      __________________________________________________________
                      Date to Effect Conversion

                      __________________________________________________________
                      Number and series of shares of Series B Preferred
                      Stock owned prior to Conversion

                      __________________________________________________________
                      Number and series of shares of Series B Preferred
                      Stock to be Converted

                      __________________________________________________________
                      Stated Value of shares of Series B Preferred Stock to be
                      Converted (including _______________ of dividends added
                      under Section 2(b) of the Registration Rights Agreement)

                      __________________________________________________________
                      Number of shares of Common Stock to be Issued

                      __________________________________________________________
                      Applicable Conversion Price

                      __________________________________________________________
                      Number and series of shares of Series B Preferred
                      Stock subsequent to Conversion


                      Name of Holder
                      By:_______________________________________________________

                      Name:_____________________________________________________

                      Title:____________________________________________________


                                       21


<PAGE>


                            CERTIFICATE OF CORRECTION
                     FILED TO CORRECT A CERTAIN ERROR IN THE
                         CERTIFICATE OF DESIGNATIONS OF
                   SERIES B-1 CONVERTIBLE PREFERRED STOCK AND
                    SERIES B-2 CONVERTIBLE PREFERRED STOCK OF
                             ASPEN TECHNOLOGY, INC.

     Aspen Technology Inc., a corporation organized and existing under the by
virtue of the General Corporation Law of the State of Delaware DOES HEREBY
CERTIFY:

     1.  The name of the corporation is Aspen Technology, Inc.

     2.  That a Certificate of Designations of Series B-1 Convertible Preferred
Stock and Series B-2 Convertible Preferred Stock was filed with the Secretary of
State of the State of Delaware on February 6, 2002, and that said Certificate
requires correction as permitted by Section 103 of the General Corporation Law
of the State of Delaware.

     3.  The inaccuracy or defect of said Certificate to be corrected is set
forth in Section 2 of the Certificate as follows:

     ""INITIAL PURCHASE PRICE" means (i) in the case of Series B-1 Preferred
Stock, $1,000, and (ii) in the case of Series B-2 Preferred Stock, the greater
of (x) the lesser of (a) the average of the daily Volume Weighted Average Prices
over the twenty (20) consecutive Trading Day period ending on February 27, 2002
(including such date) or (b) the average of the daily Volume Weighted Average
Prices over the three (3) consecutive Trading Day period ending on February 27,
2002 (including such date), or (y) $15.00 (as adjusted for any stock splits,
stock dividends, stock combinations or similar events occurring after the
Original Issue Date of the Series B-1 Preferred Stock and prior to the Original
Issue Date of the Series B-2 Preferred Stock)."

     4.  The corrected portion of Section 2 should read as follows:

     ""INITIAL PURCHASE PRICE" means (i) in the case of Series B-1 Preferred
Stock, $17.75, and (ii) in the case of Series B-2 Preferred Stock, the greater
of (x) the lesser of (a) the average of the daily Volume Weighted Average Prices
over the twenty (20) consecutive Trading Day period ending on February 27, 2002
(including such date) or (b) the average of the daily Volume Weighted Average
Prices over the three (3) consecutive Trading Day period ending on February 27,
2002 (including such date), or (y) $15.00 (as adjusted for any stock splits,
stock dividends, stock combinations or similar events occurring after the
Original Issue Date of the Series B-1 Preferred Stock and prior to the Original
Issue Date of the Series B-2 Preferred Stock)."

     IN WITNESS WHEREOF, Aspen Technology, Inc. has caused this Certificate to
be signed by its Chief Financial Officer this 12th day of February, 2002.

                                    ASPEN TECHNOLOGY, INC.

                                    By: /s/ Lisa W. Zappala
                                       ------------------------------------
                                       Lisa W. Zappala
                                       Chief Financial Officer