<PAGE>


                                                                   Exhibit 10.21


                            FIRST AMENDMENT TO LEASE

         This First Amendment to Lease dated as of March 21, 2001, PROGRESS ROAD
LLC, a Massachusetts limited liability company with a principal place of
business at 10 Waltham Street, Wilmington, Massachusetts 01887, as Landlord
("Landlord"), and PRI AUTOMATION, a Massachusetts corporation with its principal
place of business at 17 Progress Road, Billerica, Massachusetts as tenant
("Tenant").

                                   WITNESSETH:

         WHEREAS, Landlord and Tenant entered into that certain lease dated as
of October 12, 2000, (the "Lease") of that certain Building located at 17
Progress Road, Billerica, Massachusetts, as more particularly described in the
Lease (the "Premises"); and

         WHEREAS, in connection with the Landlord's construction of the Proposed
Building, Tenant has INTER ALIA requested certain revisions and additions in the
Proposed Building and changes to the existing Building which changes require
modification to the Lease as are hereafter set forth.

         NOW THEREFORE, for Ten Dollars ($10.00) and other good and valuable
consideration, the receipt and sufficiency of which is hereby acknowledged, the
Landlord and the Tenant hereby agree to amend the Lease as follows:

         1. Section 1.1. of the Lease is amended by deleting the following words
in subsection (a) "57,000 +/- rentable square feet of space" replacing the same
with the following: "58,250 rentable square feet of space which includes 1,250
feet of space in the catwalk to be constructed in the Premises at the same time
as the construction of the Proposed Building as hereinafter defined."

         2. Section 1.1 of the Lease is hereby further amended by deleting the
following words in subsection (b) "61,543 +/- rentable square feet of space" and
replacing the same with the following: "61,948 rentable square feet of space
including 7,948 square feet of space on the mezzanine".

         3. Section 1.1 of the Lease is hereby further amended by deleting the
words "118,543 rentable square feet of space" and replacing with "120,198
rentable square feet of space."

         4. Section 1.2 A is hereby amended by inserting the following paragraph
between the existing second and third paragraphs thereof

                  "Landlord and Tenant acknowledge and agree that as of the date
         hereof the Tenant has requested certain revisions to the Proposed
         Building to be constructed by Landlord which are in excess of the costs
         and the scope of the work set forth in Exhibit B to the Lease. The
         parties have agreed, by correspondence dated January 30, 2001, as
         modified by correspondence dated March 16, 2001, copies of which are
         attached hereto as Exhibit 1 and incorporated herein, the Landlord will
         include certain items denoted with the letter X under the column
         labeled Colrane Company in the scope of the work the


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         Landlord will complete under this Lease and for the items listed with a
         dollar amount shown as Numbers 5 and 8 the Landlord agrees to expend up
         to such amount listed therein as an allowance, but not a guarantee of
         the total cost of such item with the Tenant agreeing to pay for the
         cost of any overage for such item(s). Tenant agrees that the items
         which have been marked with an X will be paid for by the Tenant in
         addition to other sums due and owing by the Tenant pursuant to the
         Lease. The Tenant will pay these sums either directly to the contractor
         completing such work or to Landlord upon presentation of an invoice
         therefore, but in any event prior to taking occupancy of the Proposed
         Building. Additionally, Landlord and Tenant agree to delete the current
         Exhibit B to the Lease and replace the same with Exhibit B-1 attached
         hereto and incorporated herein."

         5. Section 3.2B(ii) is hereby amended by deleting the words "June l,
2001" and replacing the same with "September 15, 2001".

         6. Section 3.2B(iii) is hereby deleted in its entirety and replaced
with the following:

         Notwithstanding any provision of this Lease to the contrary, in the
         event that the Proposed Building is not substantially completed as
         provided in Section 3.2(c) hereof on or prior to the Deferred Delivery
         Date (as such date may be extended for reasons due to Force Majeure
         and/or to Tenant's Delay), then Tenant may elect to receive from
         Landlord as liquidated damages an abatement of Fixed Rent for the
         Proposed Building only (following the commencement of rental
         obligations pursuant to Section 4.1 hereof) equal to (a) one hundred
         percent (100%) of the Fixed Rent due for the Proposed Building for each
         day the Proposed Building is not substantially completed as provided in
         Section 3.2(c) hereof beyond the Deferred Delivery Date, as such date
         may be extended as aforesaid. The foregoing remedies shall be Tenant's
         sole and exclusive remedies for not having the Proposed Building not
         being ready for occupancy as required hereunder.

         For purposes hereof, the Deferred Delivery Date shall be September 15,
         2001 as such date may be extended for a period equal to that of (i) any
         delays due to Force Majeure, (ii) the number of delay days caused by a
         Tenant's Delay as hereinbefore determined.

         7. Section 3.3 is hereby deleted in its entirety.

         8. Section 4.2.2 is hereby deleted in its entirety and replaced with
the following:

                  "4.2.2  FIXED RENT FOR THE INITIAL TERM: The Fixed Rent for
the each Lease Year of the initial Term of this Lease shall be as follows:

                  A.  FIXED RENT AS TO EXISTING BUILDING AND RELATED PROPERTY
                      AREAS:

<TABLE>
                  <S>               <C>                  <C>
                  1st Lease Year:   $ 404,837.50/annual; $ 33,736.46/mo.
                  2nd Lease Year:   $ 404,837.50/annual; $ 33,736.46/mo.
                  3rd Lease Year:   $ 413,575.00/annual: $ 34,464.58/mo.
                  4th Lease Year:   $ 413,575.00/annual: $ 34,464.58/mo.
                  5th Lease Year:   $ 422,312.50/annual: $ 35,192.71/mo.
                  6th Lease Year:   $ 422,312.50/annual: $ 35,192.71/mo.
                  7th Lease Year:   $ 431,050.00/annual: $ 35,920.83/mo.
                  8th Lease Year:   $ 431,050.00/annual: $ 35,920.83/mo.
                  9th Lease Year:   $ 431,050.00/annual: $ 35,920.83/mo.
                  10th Lease Year:  $ 431,050.00/annual: $ 35,920.83/mo.
</TABLE>


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<PAGE>


                  B.  FIXED RENT AS TO PROPOSED BUILDING AND RELATED PROPERTY
                      AREAS:

                  Subject to the completion and delivery of the Proposed
Building as contemplated in Section 3.2 hereof, Tenant shall pay to Landlord
Fixed Rent attributable to the Proposed Building and related Property areas as
follows:

<TABLE>
                  <S>               <C>                 <C>
                  1st Lease Year:   $486,291.80/annual: $ 40,524.82/mo.
                  2nd Lease Year:   $486,291.80/annual: $ 40,524.82/mo.
                  3rd Lease Year:   $495,584.00/annual: $ 41,298.67/mo.
                  4th Lease Year:   $495,584.00/annual: $ 41,298.67/mo.
                  5th Lease Year:   $504,876.20/annual: $ 42,073.00/mo.
                  6th Lease Year:   $504,876.20/annual: $ 42,073.00/mo
                  7th Lease Year:   $514,168.40/annual: $ 42,847.37/mo.
                  8th Lease Year:   $514,168.40/annual: $ 42,847.37/mo.
                  9th Lease Year:   $514,168.40/annual: $ 42,847.37/mo.
                  10th Lease Year:  $514,168.40/annual: $ 42,847.37/mo."
</TABLE>

         9. This First Amendment to Lease may be executed in two (2) or more
counterparts, each of which shall be an original but such counterparts together
shall constitute one and the same instrument notwithstanding that both Landlord
and Tenant are not signatories to the same counterpart. Delivery of an executed
counterpart of this First Amendment to Lease by telefacsimile shall be equally
as effective as delivery of any original executed counterpart. Any party
delivering an executed counterpart of this First Amendment to Lease by
telefacsimile also shall deliver an original executed counterpart of this First
Amendment to Lease, but the failure to deliver an original executed counterpart
shall not affect the validity, enforceability and binding effect of this First
Amendment to Lease. Signature and acknowledgement pages may be detached from the
counterparts and attached to a single copy of this First Amendment to Lease to
physically form one (1) document.

         10. All other terms, conditions, covenants and provisions as appear in
the Lease are hereby ratified and confirmed and shall remain unchanged.

         WITNESS OUR HANDS AND SEAL AS OF THIS 21st DAY OF MARCH 2001.


TENANT:                                       LANDLORD:
PRI AUTOMATION                                PROGRESS ROAD LLC

---------------------------                   ---------------------------------
By:                                           By:
Its:                                          Its:



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