Document:

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                                                                 Exhibit 4.3

                       AMENDMENT NO. 1 TO RIGHTS AGREEMENT

       This Amendment No. 1 (this "Amendment"), dated as of October 22, 2001, is
by and between PRI Automation, Inc., a Massachusetts corporation (the
"Company"), and State Street Bank and Trust Company (the "Rights Agent").

       WHEREAS, the Company and the Rights Agent are parties to the Rights
Agreement, dated as of December 9, 1998 (the "Agreement");

       WHEREAS, capitalized terms used but not otherwise defined in this
Amendment shall have the meaning given them in the Agreement; and

       WHEREAS, pursuant to Section 26 of the Agreement, this Amendment is being
executed by the Company and the Rights Agent for the purpose of amending the
Agreement as set forth below.

       NOW THEREFORE, in consideration of the mutual covenants and conditions
contained herein, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

            1. In Section 22 of the Agreement, the phrase "Any successor Rights
       Agent, whether appointed by the Company or by such a court, shall be a
       corporation organized and doing business under the laws of the United
       States or of any state of the United States, in good standing, which is
       authorized under such laws to exercise stock transfer or corporate trust
       powers and is subject to supervision or examination by Federal or state
       authority and which has at the time of its appointment as Rights Agent a
       combined capital and surplus of at least $50,000,000" is hereby replaced
       in its entirety with the following:

                 Any successor Rights Agent, whether appointed by the Company or
                 by such a court, shall be a corporation or trust company
                 organized and doing business under the laws of the United
                 States or of any state of the United States, in good standing,
                 which is authorized under such laws to exercise stock transfer
                 or corporate trust powers and is subject to supervision or
                 examination by Federal or state authority and which has at the
                 time of its appointment as Rights Agent either individually or
                 with an affiliate has a combined capital and surplus of at
                 least $50,000,000

            2. In each instance where the Agreement or Exhibit B to the
       Agreement contains the terms "Series A Participating Cumulative Preferred
       Stock" such terms are hereby replaced in their entirety with the terms
       "Class One Participating Cumulative Preferred Stock";

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            3. In each instance where the Agreement or Exhibit B to the
       Agreement contains the terms "one one-hundredth (1/100th)" such terms are
       hereby replaced in their entirety with the terms "one
       one-hundred-thousandth (1/100,000th)";

            4. In each instance where the Agreement or Exhibit B to the
       Agreement contains the terms "one-hundredths (1/100ths)" such terms are
       hereby replaced in their entirety with the terms "one-hundred-thousandths
       (1/100,000ths)";

            5. In Section 7(b) of the Agreement the terms "one-hundredth
       (1/100th)" are hereby replaced in their entirety with the terms "one
       one-hundred-thousandth (1/100,000th)";

            6. Exhibit A to the Agreement is hereby replaced in its entirety by
       Exhibit A to this Amendment; and

            7. Except as specifically amended by this Amendment, the Agreement
       shall remain in full force and effect.

                                      -2-

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       IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1
to be duly executed as of the date first above written.

                                         PRI AUTOMATION INC.

                                         By: /s/ MITCHELL G. TYSON
                                            -----------------------------------
                                            Name:  Mitchell G. Tyson
                                            Title: President and CEO

                                         STATE STREET BANK AND TRUST COMPANY

                                         By: /s/ STEPHEN CESSO
                                            -----------------------------------
                                            Name:  Stephen Cesso
                                            Title:

                                      -3-

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                                                                       EXHIBIT A

                               TERMS OF CLASS ONE
                    PARTICIPATING CUMULATIVE PREFERRED STOCK
                                       OF
                              PRI AUTOMATION, INC.

       Section 1. DESIGNATION AND NUMBER OF SHARES. The shares of such series
shall be designated as "Class One Participating Cumulative Preferred Stock" (the
"Class One Preferred Stock"), $.01 par value. The number of shares initially
constituting the Class One Preferred Stock shall be 10,000; PROVIDED, HOWEVER,
that, if more than a total of 10,000 shares of Class One Preferred Stock shall
be issuable upon the exercise of Rights (the "Rights") issued pursuant to the
Rights Agreement dated as of December 9, 1998, between the Corporation and State
Street Bank and Trust Company, as Rights Agent (the "Rights Agreement"), the
Board of Directors of the Corporation, pursuant to Section 26 of Chapter 156B of
the Massachusetts General Laws, shall direct by resolution or resolutions that a
certificate be properly executed, acknowledged, filed and recorded, in
accordance with the provisions of said Section 26 thereof, providing for the
total number of shares of Class One Preferred Stock authorized to be issued to
be increased (to the extent that the Articles of Organization then permit) to
the largest number of whole shares (rounded up to the nearest whole number)
issuable upon exercise of such Rights.

       Section 2. DIVIDENDS OR DISTRIBUTIONS.

            (a) Subject to the prior and superior rights of the holders of
shares of any other series of Preferred Stock or other class of capital stock of
the Corporation ranking prior and superior to the shares of Class One Preferred
Stock with respect to dividends, the holders of shares of the Class One
Preferred Stock shall be entitled to receive, when, as and if declared by the
Board of Directors, out of the assets of the Corporation legally available
therefor, (1) quarterly dividends payable in cash on the last day of each fiscal
quarter in each year, or such other dates as the Board of Directors of the
Corporation shall approve (each such date being referred to herein as a
"Quarterly Dividend Payment Date"), commencing on the first Quarterly Dividend
Payment Date after the first issuance of a share or a fraction of a share of
Class One Preferred Stock, in the amount of $1,000.00 per whole share (rounded
to the nearest cent) less the amount of all cash dividends declared on the Class
One Preferred Stock pursuant to the following clause (2) since the immediately
preceding Quarterly Dividend Payment Date or, with respect to the first
Quarterly Dividend Payment Date, since the first issuance of any share or
fraction of a share of Class One Preferred Stock (the total of which shall not,
in any event, be less than zero) and (2) dividends payable in cash on the
payment date for each cash dividend declared on the Common Stock in an amount
per whole share (rounded to the nearest cent) equal to the Formula Number (as
hereinafter defined) then in effect times the cash dividends then to be paid on
each share of Common Stock. In addition, if the Corporation shall pay any
dividend or make any distribution on the Common Stock payable in assets,
securities or other forms of non-cash consideration (other than dividends or
distributions solely in shares of Common Stock), then, in each such case, the
Corporation shall simultaneously pay or make on each outstanding whole share of
Class One Preferred Stock a dividend or distribution in like kind equal to the
Formula Number then in effect times such dividend or distribution on each share
of the Common

                                      -4-

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Stock. As used herein, the "Formula Number" shall be 100,000; PROVIDED, HOWEVER,
that if at any time after December 9, 1998, the Corporation shall (i) declare or
pay any dividend on the Common Stock payable in shares of Common Stock or make
any distribution on the Common Stock in shares of Common Stock, (ii) subdivide
(by a stock split or otherwise) the outstanding shares of Common Stock into a
larger number of shares of Common Stock or (iii) combine (by a reverse stock
split or otherwise) the outstanding shares of Common Stock into a smaller number
of shares of Common Stock, then in each such event the Formula Number shall be
adjusted to a number determined by multiplying the Formula Number in effect
immediately prior to such event by a fraction, the numerator of which is the
number of shares of Common Stock that are outstanding immediately after such
event and the denominator of which is the number of shares of Common Stock that
are outstanding immediately prior to such event (and rounding the result to the
nearest whole number); and PROVIDED FURTHER, that, if at any time after December
9, 1998, the Corporation shall issue any shares of its capital stock in a
merger, reclassification, or change of the outstanding shares of Common Stock,
then in each such event the Formula Number shall be appropriately adjusted to
reflect such merger, reclassification or change so that each share of Class One
Preferred Stock continues to be the economic equivalent of a Formula Number of
shares of Common Stock prior to such merger, reclassification or change.

            (b) The Corporation shall declare a dividend or distribution on the
Class One Preferred Stock as provided in Section 2(a) immediately prior to or at
the same time it declares a dividend or distribution on the Common Stock (other
than a dividend or distribution solely in shares of Common Stock); PROVIDED,
HOWEVER, that, in the event no dividend or distribution (other than a dividend
or distribution in shares of Common Stock) shall have been declared on the
Common Stock during the period between any Quarterly Dividend Payment Date and
the next subsequent Quarterly Dividend Payment Date, a dividend of $1,000.00 per
whole share on the Class One Preferred Stock shall nevertheless be payable on
such subsequent Quarterly Dividend Payment Date. The Board of Directors may fix
a record date for the determination of holders of shares of Class One Preferred
Stock entitled to receive a dividend or distribution declared thereon, which
record date shall be the same as the record date for any corresponding dividend
or distribution on the Common Stock.

            (c) Dividends shall begin to accrue and be cumulative on outstanding
shares of Class One Preferred Stock from and after the Quarterly Dividend
Payment Date next preceding the date of original issue of such shares of Class
One Preferred Stock; PROVIDED, HOWEVER, that dividends on such shares which are
originally issued after the record date for the determination of holders of
shares of Class One Preferred Stock entitled to receive a quarterly dividend and
on or prior to the next succeeding Quarterly Dividend Payment Date shall begin
to accrue and be cumulative from and after such Quarterly Dividend Payment Date.
Notwithstanding the foregoing, dividends on shares of Class One Preferred Stock
which are originally issued prior to the record date for the determination of
holders of shares of Class One Preferred Stock entitled to receive a quarterly
dividend on the first Quarterly Dividend Payment Date shall be calculated as if
cumulative from and after the last day of the fiscal quarter next preceding the
date of original issuance of such shares. Accrued but unpaid dividends shall not
bear interest. Dividends paid on the shares of Class One Preferred Stock in an
amount less than the total amount of such dividends at the time accrued and
payable on such shares shall be allocated pro rata on a share-by-share basis
among all such shares at the time outstanding.

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            (d) So long as any shares of the Class One Preferred Stock are
outstanding, no dividends or other distributions shall be declared, paid or
distributed, or set aside for payment or distribution, on the Common Stock
unless, in each case, the dividend required by this Section 2 to be declared on
the Class One Preferred Stock shall have been declared.

            (e) The holders of the shares of Class One Preferred Stock shall not
be entitled to receive any dividends or other distributions except as provided
herein.

       Section 3. VOTING RIGHTS. The holders of shares of Class One Preferred
Stock shall have the following voting rights:

            (a) Each holder of Class One Preferred Stock shall be entitled to a
number of votes equal to the Formula Number then in effect for each share of
Class One Preferred Stock held of record on each matter on which holders of the
Common Stock or stockholders generally are entitled to vote, multiplied by the
maximum number of votes per share which any holder of the Common Stock or
stockholders generally then have with respect to such matter (assuming any
holding period or other requirement to vote a greater number of shares is
satisfied).

            (b) Except as otherwise provided herein or by applicable law, the
holders of shares of Class One Preferred Stock and the holders of shares of
Common Stock shall vote together as one class for the election of directors of
the Corporation and on all other matters submitted to a vote of stockholders of
the Corporation.

            (c) If, at the time of any annual meeting of stockholders for the
election of directors, the equivalent of six quarterly dividends (whether or not
consecutive) payable on any share or shares of Class One Preferred Stock are in
default, the number of directors constituting the Board of Directors of the
Corporation shall be increased by two. In addition to voting together with the
holders of Common Stock for the election of other directors of the Corporation,
the holders of record of the Class One Preferred Stock, voting separately as a
class to the exclusion of the holders of Common Stock, shall be entitled at said
meeting of stockholders (and at each subsequent annual meeting of stockholders),
unless all dividends in arrears have been paid or declared and set apart for
payment prior thereto, to vote for the election of two directors of the
Corporation, the holders of any Class One Preferred Stock being entitled to cast
a number of votes per share of Class One Preferred Stock equal to the Formula
Number. Until the default in payments of all dividends which permitted the
election of said directors shall cease to exist, any director who shall have
been so elected pursuant to the next preceding sentence may be removed at any
time, either with or without cause, only by the affirmative vote of the holders
of the shares of Class One Preferred Stock at the time entitled to cast a
majority of the votes entitled to be cast for the election of any such director
at a special meeting of such holders called for that purpose, and any vacancy
thereby created may be filled by the vote of such holders. If and when such
default shall cease to exist, the holders of the Class One Preferred Stock shall
be divested of the foregoing special voting rights, subject to revesting in the
event of each and every subsequent like default in payments of dividends. Upon
the termination of the foregoing special voting rights, the terms of office of
all persons who may have been elected directors pursuant to said special voting
rights shall forthwith terminate, and the number of directors constituting the
Board of Directors shall be reduced by two. The voting rights granted by this
Section 3(c) shall be in

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addition to any other voting rights granted to the holders of the Class One
Preferred Stock in this Section 3.

            (d) Except as provided herein, in Section 11 or by applicable law,
holders of Class One Preferred Stock shall have no special voting rights and
their consent shall not be required (except to the extent they are entitled to
vote with holders of Common Stock as set forth herein) for authorizing or taking
any corporate action.

       Section 4. CERTAIN RESTRICTIONS.

            (a) Whenever quarterly dividends or other dividends or distributions
payable on the Class One Preferred Stock as provided in Section 2 are in
arrears, thereafter and until all accrued and unpaid dividends and
distributions, whether or not declared, on shares of Class One Preferred Stock
outstanding shall have been paid in full, the Corporation shall not

                 (i) declare or pay dividends on, make any other distributions
       on, or redeem or purchase or otherwise acquire for consideration any
       shares of stock ranking junior (either as to dividends or upon
       liquidation, dissolution or winding up) to the Class One Preferred Stock;

                 (ii) declare or pay dividends on or make any other
       distributions on any shares of stock ranking on a parity (either as to
       dividends or upon liquidation, dissolution or winding up) with the Class
       One Preferred Stock, except dividends paid ratably on the Class One
       Preferred Stock and all such parity stock on which dividends are payable
       or in arrears in proportion to the total amounts to which the holders of
       all such shares are then entitled;

                 (iii) redeem or purchase or otherwise acquire for consideration
       shares of any stock ranking on a parity (either as to dividends or upon
       liquidation, dissolution or winding up) with the Class One Preferred
       Stock; PROVIDED that the Corporation may at any time redeem, purchase or
       otherwise acquire shares of any such parity stock in exchange for shares
       of any stock of the Corporation ranking junior (either as to dividends or
       upon dissolution, liquidation or winding up) to the Class One Preferred
       Stock; or

                 (iv) purchase or otherwise acquire for consideration any shares
       of Class One Preferred Stock, or any shares of stock ranking on a parity
       with the Class One Preferred Stock, except in accordance with a purchase
       offer made in writing or by publication (as determined by the Board of
       Directors) to all holders of such shares upon such terms as the Board of
       Directors, after consideration of the respective annual dividend rates
       and other relative rights and preferences of the respective series and
       classes, shall determine in good faith will result in fair and equitable
       treatment among the respective series or classes.

            (b) The Corporation shall not permit any subsidiary of the
Corporation to purchase or otherwise acquire for consideration any shares of
stock of the Corporation unless the Corporation could, under paragraph (a) of
this Section 4, purchase or otherwise acquire such shares at such time and in
such manner.

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       Section 5. LIQUIDATION RIGHTS. Upon the liquidation, dissolution or
winding up of the Corporation, whether voluntary or involuntary, no distribution
shall be made (1) to the holders of shares of stock ranking junior (either as to
dividends or upon liquidation, dissolution or winding up) to the Class One
Preferred Stock unless, prior thereto, the holders of shares of Class One
Preferred Stock shall have received an amount equal to the accrued and unpaid
dividends and distributions thereon, whether or not declared, to the date of
such payment, plus an amount equal to the greater of (x) $1,000.00 per whole
share or (y) an aggregate amount per share equal to the Formula Number then in
effect times the aggregate amount to be distributed per share to holders of
Common Stock or (2) to the holders of stock ranking on a parity (either as to
dividends or upon liquidation, dissolution or winding up) with the Class One
Preferred Stock, except distributions made ratably on the Class One Preferred
Stock and all other such parity stock in proportion to the total amounts to
which the holders of all such shares are entitled upon such liquidation,
dissolution or winding up.

       Section 6. CONSOLIDATION, MERGER, ETC. In case the Corporation shall
enter into any consolidation, merger, combination or other transaction in which
the shares of Common Stock are exchanged for or changed into other stock or
securities, cash or any other property, then in any such case the then
outstanding shares of Class One Preferred Stock shall at the same time be
similarly exchanged or changed into an amount per share equal to the Formula
Number then in effect times the aggregate amount of stock, securities, cash or
any other property (payable in kind), as the case may be, into which or for
which each share of Common Stock is exchanged or changed. In the event both this
Section 6 and Section 2 appear to apply to a transaction, this Section 6 will
control.

       Section 7. NO REDEMPTION; NO SINKING FUND.

            (a) The shares of Class One Preferred Stock shall not be subject to
redemption by the Corporation or at the option of any holder of Class One
Preferred Stock; PROVIDED, HOWEVER, that the Corporation may purchase or
otherwise acquire outstanding shares of Class One Preferred Stock in the open
market or by offer to any holder or holders of shares of Class One Preferred
Stock.

            (b) The shares of Class One Preferred Stock shall not be subject to
or entitled to the operation of a retirement or sinking fund.

       Section 8. RANKING. The Class One Preferred Stock shall rank junior to
all other classes and series of Preferred Stock of the Corporation, unless the
Board of Directors shall specifically determine otherwise in fixing the powers,
preferences and relative, participating, optional and other special rights of
the shares of such other class or series and the qualifications, limitations and
restrictions thereof.

       Section 9. FRACTIONAL SHARES. The Class One Preferred Stock shall be
issuable upon exercise of the Rights issued pursuant to the Rights Agreement in
whole shares or in any fraction of a share that is one one-hundred-thousandth
(1/100,000th) of a share or any integral multiple of such fraction which shall
entitle the holder, in proportion to such holder's fractional shares, to receive
dividends, exercise voting rights, participate in distributions and to have the
benefit of all other rights of holders of Class One Preferred Stock. In lieu of
fractional shares, the

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Corporation, prior to the first issuance of a share or a fraction of a share of
Class One Preferred Stock, may elect (1) to make a cash payment as provided in
the Rights Agreement for fractions of a share other than one
one-hundred-thousandth (1/100,000th) of a share or any integral multiple thereof
or (2) to issue depository receipts evidencing such authorized fraction of a
share of Class One Preferred Stock pursuant to an appropriate agreement between
the Corporation and a depository selected by the Corporation; PROVIDED that such
agreement shall provide that the holders of such depository receipts shall have
all the rights, privileges and preferences to which they are entitled as holders
of the Class One Preferred Stock.

       Section 10. REACQUIRED SHARES. Any shares of Class One Preferred Stock
purchased or otherwise acquired by the Corporation in any manner whatsoever
shall be retired and canceled promptly after the acquisition thereof. All such
shares shall upon their cancellation become authorized but unissued shares of
Preferred Stock, without designation as to series until such shares are once
more designated as part of a particular series by the Board of Directors
pursuant to the provisions of Article 4 of the Restated Articles of
Organization.

       Section 11. AMENDMENT. None of the powers, preferences and relative,
participating, optional and other special rights of the Class One Preferred
Stock as provided herein or in the Articles of Organization shall be amended in
any manner which would alter or change the powers, preferences, rights or
privileges of the holders of Class One Preferred Stock so as to affect them
adversely without the affirmative vote of the holders of at least 66-2/3% of the
outstanding shares of Class One Preferred Stock, voting as a separate class;
PROVIDED, HOWEVER, that no such amendment approved by the holders of at least
66-2/3% of the outstanding shares of Class One Preferred Stock shall be deemed
to apply to the powers, preferences, rights or privileges of any holder of
shares of Class One Preferred Stock originally issued upon exercise of the
Rights after the time of such approval without the approval of such holder.

                                    * * * * *

                                      -9-<Page>

                                                                   Exhibit 4.4

                       AMENDMENT NO. 2 TO RIGHTS AGREEMENT

       This Amendment No. 2 (this "Amendment"), dated as of October 23, 2001, is
by and between PRI Automation, Inc., a Massachusetts corporation (the
"Company"), and State Street Bank and Trust Company (the "Rights Agent").

       WHEREAS, the Company and the Rights Agent are parties to the Rights
Agreement, dated as of December 9, 1998, as amended by Amendment No. 1 to Rights
Agreement dated as of October 22, 2001 (the "Agreement");

       WHEREAS, capitalized terms used but not otherwise defined in this
Amendment shall have the meaning given them in the Agreement;

       WHEREAS, the board of directors of the Company has approved a certain
Agreement and Plan of Merger (the "Merger Agreement") by and among the Company,
Brooks Automation, Inc., a Delaware corporation ("Brooks"), and Pontiac
Acquisition Corp., a Massachusetts corporation wholly owned by Brooks ("Brooks
Merger Sub") (Brooks and Brooks Merger Sub are collectively referred to herein
as the "Other Parties") at a meeting of the board of directors of the Company
held on October 23, 2001 (the "Meeting"), pursuant to which Brooks Merger Sub
will be merged with and into the Company (the "Merger"), and the stockholders of
the Company will become stockholders of Brooks;

       WHEREAS, upon the effectiveness of the Merger, the Other Parties
collectively will acquire more than 20% of the outstanding shares of the
Company's Common Stock, $.01 par value per share (the "Company's Common Stock");

       WHEREAS, the acquisition of more than 20% of the outstanding shares of
the Company's Common Stock would result in the acquiring entity or entities
being deemed to be an "Acquiring Person" under the Rights Agreement, which would
trigger certain events pursuant to the terms of the Rights Agreement;

       WHEREAS, at the Meeting the board of directors of the Company determined
that it is in the best interest of the Company to amend the Rights Agreement
prior to the Company entering into the Merger Agreement so that the Other
Parties will not thereby become Acquiring Persons under the Rights Agreement;
and

       WHEREAS, pursuant to Section 26 of the Agreement, this Amendment is being
executed by the Company and the Rights Agent for the purpose of amending the
Agreement as set forth below.

       NOW THEREFORE, in consideration of the mutual covenants and conditions
contained herein, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

                                       1

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       1. The first subparagraph of Section 1, definition of "Acquiring Person,"
is hereby amended by addition thereto of the following final sentence:

            Anything to the contrary in this paragraph notwithstanding, the term
            "Acquiring Person" shall not include either of Brooks Automation,
            Inc., a Delaware corporation ("Brooks"), or Pontiac Acquisition
            Corp., a Massachusetts corporation wholly owned by Brooks ("Brooks
            Merger Sub") (Brooks and Brooks Merger Sub are collectively referred
            to herein as the "Other Parties"), if and only if, any of such Other
            Parties individually or collectively shall become the Beneficial
            Owner of 20% or more of the Common Shares of the Company then
            outstanding as a result of the execution of the Agreement and Plan
            of Merger authorized and approved by the Board of Directors of the
            Company at the meeting of the Board of Directors held on October 23,
            2001, as it may be amended from time to time (the "Merger
            Agreement"), or the consummation of the transactions contemplated
            thereby, and/or any options to purchase or proxies or agreements to
            vote Common Shares of the Company granted by the Company or any
            stockholder of the Company to the Other Parties in connection with
            the Merger Agreement or any agreements or arrangements entered into
            by the Company and the Other Parties in connection therewith.

       2. Except as specifically amended by this Amendment, the Agreement shall
remain in full force and effect.

                                       2

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       IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 2
to be duly executed as of the date first above written.

                                         PRI AUTOMATION INC.

                                         By: /s/ MITCHELL G. TYSON
                                            -----------------------------------
                                            Name:  Mitchell G. Tyson
                                            Title: President and CEO

                                         STATE STREET BANK AND TRUST COMPANY

                                         By: /s/ STEPHEN CESSO
                                            -----------------------------------
                                            Name:  Stephen Cesso
                                            Title:

                                       3

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