Document:

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                                                                   EXHIBIT 10.12

                                   Agreement
                                   ---------

     This Agreement is entered into as of this 18th day of May, 2000, between
Parametric Technology Corporation, a Massachusetts corporation (the "Company"),
and James E. Heppelmann ("Heppelmann").

     WHEREAS, Heppelmann is the Senior Vice President, Windchill; and

     WHEREAS, to provide incentive for Heppelmann to maintain employment with
the Company, the Company desires to make the following arrangements with
Heppelmann concerning his termination of employment.

     NOW, THEREFORE, the Company and Heppelmann hereby agree as follows:

     1.  Termination Notice.  The Company agrees that it may not terminate the
         ------------------
employment of Heppelmann unless (i) such termination is for Cause (as defined
below) or (ii) the Company has delivered to Heppelmann a written notice of such
termination (the "Termination Notice") at least six months in advance of the
termination date. The duties of Heppelmann during the period from the date of
delivery of a Termination Notice until the termination of his employment shall
be as determined by the Board of Directors or the Chief Executive Officer.

     2.  Salary.  During the period from the date of delivery of the
         ------
Termination Notice (the "Notice Date") until the earlier of (i) the date six
months after the Notice Date or (ii) the date Heppelmann commences employment
with another company or organization, the Company shall pay to Heppelmann a
salary that is equal, on an annualized basis, to the highest annual salary
(excluding any bonuses) in effect with respect to Heppelmann during the six-
month period immediately preceding the Termination Notice.

     3.  Stock Options.  Effective upon a Change in Control (as defined below)
         -------------
of the Company, all stock options granted to Heppelmann and then outstanding
under any Stock Option Plan (as defined below) of the Company shall become
exercisable in full, notwithstanding any vesting schedule or other provisions to
the contrary in the agreements evidencing such options; and the Company and
Heppelmann hereby agree that such option agreements are hereby and will be
deemed amended to give effect to this provision.

     4.  Definitions.
         -----------

         (a)  A termination by the Company of Heppelmann's employment for
"Cause" shall mean termination (i) for Heppelmann's willful and continued
failure to substantially perform his duties to the Company
<PAGE>

(other than any such failure resulting from Heppelmann's incapacity due to
physical or mental illness), provided that (a) the Company has delivered a
written demand for substantial performance to Heppelmann specifically
identifying the manner in which the Company believes that Heppelmann has not
substantially performed his duties, and (b) Heppelmann has not cured such
failure within 30 days after such demand, (ii) for willful conduct by Heppelmann
which is demonstrably and materially injurious to the Company, or (iii) for
Heppelmann's willful violation of any material provision of any confidentiality,
nondisclosure, assignment of invention, noncompetition or similar agreement
entered into by Heppelmann in connection with his employment by the Company. For
purposes of this paragraph, no act or failure to act on Heppelmann's part shall
be deemed "willful" unless done or omitted to be done by Heppelmann not in good
faith and without reasonable belief that his action or omission was in the best
interests of the Company.

          (b)  A "Change in Control" of the Company shall mean the occurrence of
any of the following events: (i) any "person", as such term is used in Sections
13(d) and 14(d) of the Securities Exchange Act of 1934, as amended (the
"Exchange Act") (other than the Company, any trustee or other fiduciary holding
securities under an employee benefit plan of the Company, or any corporation
owned directly or indirectly by the stockholders of the Company in substantially
the same proportion as their ownership of stock in the Company) is or becomes
the "beneficial owner" (as defined in Rule 13d-3 under the Exchange Act),
directly or indirectly, of securities of the Company representing 50% or more of
the combined voting power of the Company's then outstanding securities (other
than as a result of acquisitions of such securities from the Company); (ii)
individuals who, as of the date hereof, constitute the Board of Directors of the
Company (the "Incumbent Board") cease for any reason to constitute at least a
majority of the Board, provided that any person becoming a director subsequent
to the date hereof whose election, or nomination for election by the Company's
stockholders, was approved by a vote of at least a majority of the directors
then comprising the Incumbent Board (other than an election or nomination of an
individual whose initial assumption of office is in connection with an actual or
threatened election contest relating to the election of the directors of the
Company) shall be, for purposes of this Agreement, considered to be a member of
the Incumbent Board; (iii) the stockholders of the Company approve a merger or
consolidation of the Company with any other corporation, other than (A) a merger
or consolidation which would result in the voting securities of the Company
outstanding immediately

                                       2
<PAGE>

prior thereto continuing to represent (either by remaining outstanding or by
being converted into voting securities of the surviving entity) more than 50% of
the combined voting power of the voting securities of the Company or such
surviving entity outstanding immediately after such merger or consolidation or
(B) a merger or consolidation effected to implement a recapitalization of the
Company (or similar transaction) in which no "person" (as defined above)
acquires more than 20% of the combined voting power of the Company's then
outstanding securities; or (iv) the stockholders of the Company approve a plan
of complete liquidation of the Company.

(c)  A "Stock Option Plan" of the Company shall mean any stock option or equity
compensation plan of the Company in effect at any time, including without
limitation the 1987 Incentive Stock Option Plan, the 1997 Incentive Stock Option
Plan 1997, the 1997 Non-statutory Stock Option Plan and the 2000 Equity
Incentive Plan.

     5.   Term.   This Agreement shall continue in effect until February 28,
          ----
2003, unless extended by the mutual written consent of the Company and
Heppelmann.
     6.   Successors.
          ----------
          (a)     This Agreement is personal to Heppelmann and without the prior
written consent of the Company shall not be assignable by Heppelmann otherwise
than by will or the laws of descent and distribution.
          (b)     This Agreement shall inure to the benefit of and be binding
upon the Company and its successors and assigns.
          (c)     The Company will require any successor (whether direct or
indirect, by purchase, merger, consolidation or otherwise) to all or
substantially all of the business and/or assets of the Company to assume
expressly and agree to perform this Agreement in the same manner and to the same
extent that the Company would be required to perform it if no such succession
had taken place. As used in this Agreement, "Company" shall mean the Company as
defined above and any successor to its business and/or assets as aforesaid which
assumes and agrees to perform this Agreement.

     7.   Miscellaneous.
          -------------
          (a)     This Agreement shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts, without reference
to principles of conflict of laws.

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<PAGE>

          (b)  This Agreement may not be amended or modified otherwise than by a
written agreement executed by the parties hereto or their respective successors
and legal representatives.
          (c)  All notices and other communications hereunder shall be in
writing and shall be delivered by hand delivery, by a reputable overnight
courier service, or by registered or certified mail, return receipt requested,
postage prepaid, in each case addressed as follows:

     If to the Company:
     -----------------

     Parametric Technology Corporation
     128 Technology Drive
     Waltham, MA 02453
     Attention: Senior Vice President - General Counsel

     If to Heppelmann:
     -----------------

     James E. Heppelmann
     2 Ridge Road
     Framingham, MA 01710

or to such other address as either party shall have furnished to the other in
writing in accordance herewith. Any notice or communication shall be deemed to
be delivered upon the date of hand delivery, one day following delivery to such
overnight courier service, or three days following mailing by registered or
certified mail.

     EXECUTED as of the date first written above.

                         PARAMETRIC TECHNOLOGY CORPORATION

                         By:   /s/ C. Richard Harrison
                              ------------------------
                              C. Richard Harrison
                              President and Chief Executive Officer

                               /s/ James E. Heppelmann
                              ------------------------
                              James E. Heppelmann

                                       4<PAGE>

                                                                   EXHIBIT 10.13

                                   Agreement
                                   ---------

     This Agreement is entered into as of this 18th day of May, 2000, between
Parametric Technology Corporation, a Massachusetts corporation (the "Company"),
and Jon R. Stevenson ("Stevenson").

     WHEREAS, Stevenson is the Executive Vice President, General Manager - MCAD;
and

     WHEREAS, to provide incentive for Stevenson to maintain employment with the
Company, the Company desires to make the following arrangements with Stevenson
concerning his termination of employment.

     NOW, THEREFORE, the Company and Stevenson hereby agree as follows:

     1.  Termination Notice.   The Company agrees that it may not terminate the
         ------------------
employment of Stevenson unless (i) such termination is for Cause (as defined
below) or (ii) the Company has delivered to Stevenson a written notice of such
termination (the "Termination Notice") at least six months in advance of the
termination date.  The duties of Stevenson during the period from the date of
delivery of a Termination Notice until the termination of his employment shall
be as determined by the Board of Directors or the Chief Executive Officer.

     2.  Salary.   During the period from the date of delivery of the
         ------
Termination Notice (the "Notice Date") until the earlier of (i) the date six
months after the Notice Date or (ii) the date Stevenson commences employment
with another company or organization, the Company shall pay to Stevenson a
salary that is equal, on an annualized basis, to the highest annual salary
(excluding any bonuses) in effect with respect to Stevenson during the six-month
period immediately preceding the Termination Notice.

     3.  Stock Options.   Effective upon a Change in Control (as defined below)
         -------------
of the Company, all stock options granted to Stevenson and then outstanding
under any Stock Option Plan (as defined below) of the Company shall become
exercisable in full, notwithstanding any vesting schedule or other provisions to
the contrary in the agreements evidencing such options; and the Company and
Stevenson hereby agree that such option agreements are hereby and will be deemed
amended to give effect to this provision.

     4.  Definitions.
         -----------

          (a)  A termination by the Company of Stevenson's employment for
"Cause" shall mean termination (i) for Stevenson's willful and continued failure
to substantially perform his duties to the Company (other than any such failure
resulting from Stevenson's incapacity due to physical or mental illness),
provided that
<PAGE>

(a) the Company has delivered a written demand for substantial performance to
Stevenson specifically identifying the manner in which the Company believes that
Stevenson has not substantially performed his duties, and (b) Stevenson has not
cured such failure within 30 days after such demand, (ii) for willful conduct by
Stevenson which is demonstrably and materially injurious to the Company, or
(iii) for Stevenson's willful violation of any material provision of any
confidentiality, nondisclosure, assignment of invention, noncompetition or
similar agreement entered into by Stevenson in connection with his employment by
the Company. For purposes of this paragraph, no act or failure to act on
Stevenson's part shall be deemed "willful" unless done or omitted to be done by
Stevenson not in good faith and without reasonable belief that his action or
omission was in the best interests of the Company.

          (b)  A "Change in Control" of the Company shall mean the occurrence of
any of the following events: (i) any "person", as such term is used in Sections
13(d) and 14(d) of the Securities Exchange Act of 1934, as amended (the
"Exchange Act") (other than the Company, any trustee or other fiduciary holding
securities under an employee benefit plan of the Company, or any corporation
owned directly or indirectly by the stockholders of the Company in substantially
the same proportion as their ownership of stock in the Company) is or becomes
the "beneficial owner" (as defined in Rule 13d-3 under the Exchange Act),
directly or indirectly, of securities of the Company representing 50% or more of
the combined voting power of the Company's then outstanding securities (other
than as a result of acquisitions of such securities from the Company); (ii)
individuals who, as of the date hereof, constitute the Board of Directors of the
Company (the "Incumbent Board") cease for any reason to constitute at least a
majority of the Board, provided that any person becoming a director subsequent
to the date hereof whose election, or nomination for election by the Company's
stockholders, was approved by a vote of at least a majority of the directors
then comprising the Incumbent Board (other than an election or nomination of an
individual whose initial assumption of office is in connection with an actual or
threatened election contest relating to the election of the directors of the
Company) shall be, for purposes of this Agreement, considered to be a member of
the Incumbent Board; (iii) the stockholders of the Company approve a merger or
consolidation of the Company with any other corporation, other than (A) a merger
or consolidation which would result in the voting securities of the Company
outstanding immediately prior thereto continuing to represent (either by
remaining outstanding or by being converted into voting

                                       2
<PAGE>

securities of the surviving entity) more than 50% of the combined voting power
of the voting securities of the Company or such surviving entity outstanding
immediately after such merger or consolidation or (B) a merger or consolidation
effected to implement a recapitalization of the Company (or similar transaction)
in which no "person" (as defined above) acquires more than 20% of the combined
voting power of the Company's then outstanding securities; or (iv) the
stockholders of the Company approve a plan of complete liquidation of the
Company.

(c)  A "Stock Option Plan" of the Company shall mean any stock option or equity
compensation plan of the Company in effect at any time, including without
limitation the 1987 Incentive Stock Option Plan, the 1997 Incentive Stock Option
Plan 1997, the 1997 Non-statutory Stock Option Plan and the 2000 Equity
Incentive Plan.

     5.   Term.   This Agreement shall continue in effect until February 28,
          ----
2003, unless extended by the mutual written consent of the Company and
Stevenson.

     6.   Successors.
          ----------

          (a)     This Agreement is personal to Stevenson and without the prior
written consent of the Company shall not be assignable by Stevenson otherwise
than by will or the laws of descent and distribution.

          (b)     This Agreement shall inure to the benefit of and be binding
upon the Company and its successors and assigns.

          (c)     The Company will require any successor (whether direct or
indirect, by purchase, merger, consolidation or otherwise) to all or
substantially all of the business and/or assets of the Company to assume
expressly and agree to perform this Agreement in the same manner and to the same
extent that the Company would be required to perform it if no such succession
had taken place.  As used in this Agreement, "Company" shall mean the Company as
defined above and any successor to its business and/or assets as aforesaid which
assumes and agrees to perform this Agreement.

     7.   Miscellaneous.
          -------------

          (a)     This Agreement shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts, without reference
to principles of conflict of laws.

          (b)     This Agreement may not be amended or modified otherwise than
by a written agreement executed by the parties hereto or their respective
successors and legal representatives.

                                       3
<PAGE>

          (c)       All notices and other communications hereunder shall be in
writing and shall be delivered by hand delivery, by a reputable overnight
courier service, or by registered or certified mail, return receipt requested,
postage prepaid, in each case addressed as follows:

     If to the Company:
     -----------------

     Parametric Technology Corporation
     128 Technology Drive
     Waltham, MA 02453
     Attention:  Senior Vice President - General Counsel

     If to Stevenson:
     ----------------

     Jon R. Stevenson
     12 Petersen Circle
     Sudbury, MA 01776

or to such other address as either party shall have furnished to the other in
writing in accordance herewith. Any notice or communication shall be deemed to
be delivered upon the date of hand delivery, one day following delivery to such
overnight courier service, or three days following mailing by registered or
certified mail.

     EXECUTED as of the date first written above.

                         PARAMETRIC TECHNOLOGY CORPORATION

                         By:  /s/  C. Richard Harrison
                              ----------------------------------------
                              C. Richard Harrison
                              President and Chief Executive Officer

                              /s/ Jon R. Stevenson
                              ----------------------------------------
                              Jon R. Stevenson

                                       4

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