SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                    FORM 10-Q


         (MARK ONE)

[X]      QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
         SECURITIES EXCHANGE ACT OF 1934


                  For the quarterly period ended March 31, 2002

                                       or

[ ]     TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
        SECURITIES EXCHANGE ACT OF 1934


For the transition period from _______________ to _______________


Commission file number 0-23621


                              MKS INSTRUMENTS, INC.

             (Exact name of registrant as specified in its charter)


Massachusetts                                             04-2277512
(State or other jurisdiction                              (I.R.S. Employer
of incorporation or organization)                         Identification No.)

Six Shattuck Road, Andover, Massachusetts                 01810
(Address of principal executive offices)                  (Zip Code)

Registrant's telephone number, including area code        (978) 975-2350

      Indicate by check mark whether the registrant: (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes X No __.

Number of shares outstanding of the issuer's common stock as of April 30, 2002:
51,099,212


                              MKS INSTRUMENTS, INC.
                                    FORM 10-Q
                                      INDEX

PART I            FINANCIAL INFORMATION

         ITEM 1.  FINANCIAL STATEMENTS

                           Consolidated Balance Sheets  -
                           March 31, 2002 and December 31, 2001

                           Consolidated Statements of Income   -
                           Three months ended March 31, 2002 and 2001

                           Consolidated Statements of Cash Flows -
                           Three months ended March 31, 2002 and 2001

                           Notes to Consolidated Financial Statements

         ITEM 2.  MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION
                  AND RESULTS OF OPERATIONS

         ITEM 3.  QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

PART II  OTHER INFORMATION

         ITEM 1.  LEGAL PROCEEDINGS

         ITEM 2.  CHANGES IN SECURITIES AND USE OF PROCEEDS

         ITEM 3.  DEFAULTS UPON SENIOR SECURITIES

         ITEM 4.  SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

         ITEM 5.  OTHER INFORMATION

         ITEM 6.  EXHIBITS AND REPORTS ON FORM 8-K


                                                                               2

PART I.  FINANCIAL INFORMATION

         ITEM 1.  FINANCIAL STATEMENTS

                              MKS INSTRUMENTS, INC.
                           CONSOLIDATED BALANCE SHEETS
                        (in thousands, except share data)



                                                                                         March 31, 2002        December 31, 2001
                                                                                         --------------        -----------------
                                                                                          (Unaudited)
                                      ASSETS
Current assets:
                                                                                                         
    Cash and cash equivalents......................................................        $   97,120               $ 120,869
    Short-term investments.........................................................            31,682                  16,625
    Trade accounts receivable, net.................................................            49,661                  35,778
    Inventories....................................................................            79,104                  56,954
    Deferred tax asset.............................................................            20,285                  16,426
    Other current assets...........................................................            13,094                  16,353
                                                                                            ---------              ----------
        Total current assets.......................................................           290,946                 263,005
    Property, plant and equipment, net.............................................            86,325                  69,634
    Goodwill and acquired intangible assets, net...................................           316,120                  52,285
    Long-term investments..........................................................            12,883                  11,029
    Other assets...................................................................            13,674                  15,236
                                                                                            ---------              ----------
        Total assets...............................................................        $  719,948               $ 411,189
                                                                                            =========               =========

                       LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
    Short-term borrowings..........................................................        $   10,651               $   9,238
    Current portion of long-term debt..............................................             4,817                   5,074
    Current portion of capital lease obligations...................................               459                     503
    Accounts payable...............................................................            16,763                   9,668
    Accrued compensation...........................................................             7,765                   6,116
    Other accrued expenses.........................................................            26,413                  15,551
                                                                                               ------                  ------
        Total current liabilities..................................................            66,868                  46,150
Long-term debt.....................................................................            15,442                  10,916
Long-term portion of capital lease obligations.....................................               263                     341
Deferred tax liability.............................................................            11,378                     ---
Other liabilities..................................................................               784                     911
Commitments and contingencies
Stockholders' equity:
    Preferred Stock, $0.01 par value, 2,000,000 shares
        authorized; none issued and outstanding....................................               ---                     ---
    Common Stock, no par value, 75,000,000 shares authorized;
        50,974,344 and 37,998,699 issued and outstanding at
        March 31, 2002 and December 31, 2001, respectively.........................               113                     113
    Additional paid-in capital.....................................................           569,932                 285,252
    Retained earnings..............................................................            56,373                  68,160
    Accumulated other comprehensive loss...........................................            (1,205)                   (654)
                                                                                            ---------              ----------
        Total stockholders' equity.................................................           625,213                 352,871
                                                                                             --------                --------
        Total liabilities and stockholders' equity.................................         $ 719,948               $ 411,189
                                                                                            =========               =========





   The accompanying notes are an integral part of the consolidated financial
                                  statements.


                                                                               3

                              MKS INSTRUMENTS, INC.
                        CONSOLIDATED STATEMENTS OF INCOME
                      (in thousands, except per share data)
                                   (Unaudited)



                                                                      Three Months Ended
                                                                           March 31,
                                                                    2002               2001
                                                                 ---------           ---------
                                                                               
Net sales .............................................          $  59,067           $ 110,888
Cost of sales .........................................             39,847              67,693
                                                                 ---------           ---------
Gross profit ..........................................             19,220              43,195
Research and development ..............................              9,132              11,151
Selling, general and administrative ...................             17,058              19,057
Amortization of goodwill and acquired intangible assets              2,205               2,240
Goodwill impairment charge ............................                 --               3,720
Merger expenses .......................................                 --               7,708
Purchase of in-process research and development .......              6,100                  --
                                                                 ---------           ---------
Loss from operations ..................................            (15,275)               (681)
Interest expense ......................................                329                 402
Interest income .......................................                755               1,794
                                                                 ---------           ---------
Income (loss) before income taxes .....................            (14,849)                711
Provision (benefit) for income taxes ..................             (3,062)              2,816
                                                                 ---------           ---------
Net loss ..............................................          $ (11,787)          $  (2,105)
                                                                 =========           =========

Net loss per share:
    Basic and diluted .................................          $   (0.25)          $   (0.06)
                                                                 =========           =========

Weighted average common shares outstanding:
    Basic and diluted .................................             46,288              36,820
                                                                 =========           =========














   The accompanying notes are an integral part of the consolidated financial
                                  statements.


                                                                               4

                              MKS INSTRUMENTS, INC.
                      CONSOLIDATED STATEMENTS OF CASH FLOWS
                                 (in thousands)
                                   (Unaudited)



                                                                                                        Three Months Ended
                                                                                                             March 31,
                                                                                                      2002                 2001
                                                                                                   --------             --------
Cash flows from operating activities:
                                                                                                                  
    Net loss............................................................................          $ (11,787)            $ (2,105)
    Adjustments to reconcile net loss to net cash provided by (used in)
      operating activities:
         Depreciation and amortization..................................................              5,612                4,958
         Goodwill impairment charge.....................................................                ---                3,720
         Purchase of in-process research and development................................              6,100                  ---
         Other..........................................................................                 62                   27
         Changes in operating assets and liabilities net of effects of
           businesses acquired:
             Trade accounts receivable..................................................            (10,325)              14,220
             Inventories................................................................             (1,775)                (875)
             Other current assets.......................................................              5,401               (1,232)
             Accrued expenses and other current liabilities.............................                577              (13,155)
             Accounts payable...........................................................              3,344               (3,590)
                                                                                                   --------             --------
    Net cash provided by (used in) operating activities.................................             (2,791)               1,968
                                                                                                   --------             --------
    Cash flows from investing activities:
        Purchases of short-term and long-term investments...............................            (37,731)              (8,718)
        Maturities and sales of short-term and long-term investments....................             20,647                3,325
        Purchases of property, plant and equipment......................................             (1,335)              (4,898)
        Increase in other assets........................................................                 37                 (408)
        Purchases of businesses, net of cash acquired...................................             (5,716)                 ---
                                                                                                   --------             --------
    Net cash used in investing activities...............................................            (24,098)             (10,699)
                                                                                                   --------             --------
    Cash flows from financing activities:
        Proceeds from short-term borrowings.............................................              1,505               11,825
        Payments on short-term borrowings...............................................                ---              (10,988)
        Principal payments on long-term debt............................................               (684)                (695)
        Proceeds from exercise of stock options.........................................              2,610                  796
        Principal payments under capital lease obligations..............................               (121)                (250)
                                                                                                   --------             --------
    Net cash provided by financing activities...........................................              3,310                  688
                                                                                                   --------             --------
    Effect of exchange rate changes on cash and cash equivalents........................               (170)                (474)
                                                                                                   --------             --------
    Decrease in cash and cash equivalents...............................................            (23,749)              (8,517)
    Cash and cash equivalents at beginning of period....................................            120,869              123,082
    Effect of excluded results of ASTeX.................................................                ---               (3,142)
                                                                                                   --------             --------
    Cash and cash equivalents at end of period..........................................          $  97,120          $   111,423
                                                                                                   ========             ========
    Supplemental disclosure of cash flow information:
        Cash paid during the period for:
           Interest.....................................................................          $     129          $       365
                                                                                                   ========             ========
           Income taxes.................................................................          $   1,517          $     5,053
                                                                                                   ========             ========
        Noncash transactions during the period:
           Stock issued for acquisitions................................................          $ 282,341          $       ---
                                                                                                   ========             ========






   The accompanying notes are an integral part of the consolidated financial
                                  statements.


                                                                               5

                              MKS INSTRUMENTS, INC.
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                  (Tables in thousands, except per share data)

1)       Basis of Presentation
         The interim financial data as of March 31, 2002 and for the three
         months ended March 31, 2002 and 2001 is unaudited; however, in the
         opinion of MKS Instruments, Inc., the interim data includes all
         adjustments, consisting only of normal recurring adjustments, necessary
         for a fair statement of the results for the interim periods. The terms
         "MKS" and the "Company" refer to MKS Instruments, Inc. and its
         subsidiaries. The unaudited financial statements presented herein have
         been prepared in accordance with the instructions to Form 10-Q and do
         not include all the information and note disclosures required by
         generally accepted accounting principles. The financial statements
         should be read in conjunction with the December 31, 2001 audited
         financial statements and notes thereto included in the MKS Annual
         Report on Form 10-K filed with the Securities and Exchange Commission
         on April 1, 2002.

2)       Use of Estimates
         The consolidated financial statements have been prepared in accordance
         with accounting principles generally accepted in the United States. The
         preparation of these financial statements requires management to make
         estimates and assumptions that affect the reported amounts of assets
         and liabilities and the disclosure of contingent liabilities at the
         date of the financial statements and the reported amounts of revenues
         and expenses during the reporting period. On an on-going basis,
         management evaluates its estimates and judgments, including those
         related to revenue recognition, in-process research and development,
         merger expenses, intangible assets and goodwill, inventories and
         investments. Management bases its estimates and judgments on historical
         experience and on various other factors that are believed to be
         reasonable under the circumstances, the results of which form the basis
         for making judgments about the carrying values of assets and
         liabilities that are not readily apparent from other sources. Actual
         results may differ from these estimates under different assumptions or
         conditions.

3)       Recent Accounting Pronouncements
         In July 2001, the Financial Accounting Standards Board issued Statement
         of Financial Accounting Standards No. 142, "Goodwill and Other
         Intangible Assets" ("SFAS 142"), which is effective for fiscal years
         beginning after December 15, 2001. SFAS 142 requires, among other
         things, the discontinuance of goodwill amortization. In addition, the
         standard includes provisions upon adoption for the reclassification of
         certain existing recognized intangibles such as goodwill, reassessment
         of the useful lives of existing recognized intangibles,
         reclassification of certain intangibles out of previously reported
         goodwill and the testing for impairment of existing goodwill and other
         intangibles. The impairment review will involve a two-step process as
         follows:

              Step 1 -- The Company will compare the fair value of its reporting
              units to the carrying value, including goodwill, of each of those
              units. For each reporting unit where the carrying value, including
              goodwill, exceeds the unit's fair value, the Company will move on
              to step 2. If a unit's fair value exceeds the carrying value, no
              further work is performed and no impairment charge will be
              necessary.

              Step 2 -- The Company will perform an allocation of the fair value
              of the reporting unit to its identifiable tangible and
              non-goodwill intangible assets and liabilities. This will derive
              an implied fair value for the reporting unit's goodwill. The
              Company will then compare the implied fair value of the reporting
              unit's goodwill with the carrying amount of the reporting unit's
              goodwill. If the carrying amount of the reporting unit's goodwill
              is greater than the implied fair value of its goodwill, an
              impairment loss must be recognized for the excess.

         The Company is currently in the process of performing the transitional
         impairment test of its goodwill and expects to complete this review by
         the end of the second quarter of 2002.






                                                                               6

                              MKS INSTRUMENTS, INC.
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                  (Tables in thousands, except per share data)

         In accordance with SFAS 142, the Company ceased amortizing goodwill on
         January 1, 2002 and reassessed the classification of its goodwill and
         other intangible assets. This analysis, which was completed during the
         quarter ended March 31, 2002, resulted in the reclassification of
         $2,023,000 of workforce intangibles to goodwill. Also, in accordance
         with this statement, the Company reassessed the useful lives of its
         amortizable intangible assets and determined that the lives were
         appropriate.

         The following is the pro forma effect on net loss and net loss per
         share had SFAS No. 142 been in effect for the three months ended March
         31, 2001:




                                                                                                    March 31,
                                                                                                      2001
                                                                                                    -------
                                                                                                
         Net loss.........................................................................         $ (2,105)
         Add back: Impact of goodwill amortization, net of taxes..........................              910
                                                                                                    -------
         Pro forma net loss...............................................................         $ (1,195)
                                                                                                   ========

         Basic and diluted net loss per share.............................................         $  (0.06)
         Add Back: Impact of goodwill amortization, net of taxes..........................             0.03
                                                                                                    -------
         Pro forma basic and diluted net loss per share...................................         $  (0.03)
                                                                                                   ========





         Amortizable intangible assets consist of the following as of March 31,
         2002:



                                                                                                        Net
                                                           Gross Carrying        Accumulated          Carrying      Weighted Average
                                                               Amount            Amortization          Amount           Useful Life
                                                               ------            ------------          ------           -----------

                                                                                                        
         Completed technology..........................         $57,941                $6,119          $51,822                    5
         Customer relationships........................           6,803                 1,043            5,760                    7
         Other.........................................           9,081                 1,853            7,228                    6
                                                                -------                ------          -------                 ----
                                                                $73,825                $9,015          $64,810                    5
                                                                =======                ======          =======                 ====


         Amortizable intangible assets consist of the following as of December
         31, 2001:



                                                                                                                         Net
                                                                              Gross Carrying     Accumulated           Carrying
                                                                                  Amount         Amortization           Amount
                                                                                  ------         ------------           ------
                                                                                                             
         Completed technology..........................                            $16,564           $4,402            $12,162
         Customer relationships........................                              4,040              851              3,189
         Other.........................................                              8,132            2,311              5,821
                                                                                     -----            -----            -------
                                                                                   $28,736           $7,564            $21,172
                                                                                   =======           ======            =======



                                                                               7

                              MKS INSTRUMENTS, INC.
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                  (Tables in thousands, except per share data)

         Aggregate amortization expense related to acquired intangibles for the
         quarter ended March 31, 2002 was $2,205,000. Estimated amortization
         expense related to acquired intangibles for each of the five succeeding
         fiscal years is as follows:



                               Year                  Amount
                               ----                  ------
                                              
                               2002                 $12,801
                               2003                  12,664
                               2004                  12,340
                               2005                  11,439
                               2006                   9,338


4)       Cash and Cash Equivalents and Investments
         Cash and Cash equivalents consist of the following:



                                                                                                  March 31,            December 31,
                                                                                                   2002                    2001
                                                                                                                  
         Cash and Money Market Instruments...............................................         $ 41,620              $ 101,045
         Commercial Paper................................................................           37,667                  8,094
         Federal Government and Government Agency Obligations............................           10,047                 11,730
         State and Municipal Government Obligations......................................            2,789                    ---
         Corporate Obligations...........................................................            4,997                    ---
                                                                                                  --------              ---------
                                                                                                  $ 97,120              $ 120,869
                                                                                                  ========              =========


         Short-term available-for-sale investments at market value maturing
         within one year consist of the following:



                                                                                                  March 31,             December 31,
                                                                                                   2002                      2001
                                                                                                                  
         Federal Government and Government Agency Obligations............................         $ 29,757               $  5,442
         State and Municipal Government Obligations......................................            1,337                  3,100
         Corporate Obligations...........................................................              588                    ---
         Commercial Paper................................................................              ---                  8,083
                                                                                                  --------               --------
                                                                                                  $ 31,682               $ 16,625
                                                                                                  ========               ========


         Long-term available-for-sale investments at market value with
         maturities of 1 to 5 years consist of the following:



                                                                                                 March 31,             December 31,
                                                                                                   2002                    2001
                                                                                                                 
         Federal Government and Government Agency Obligations............................        $   6,018             $   1,008
         State and Municipal Government Obligations......................................              ---                 7,021
         Corporate Obligations...........................................................            6,865                 3,000
                                                                                                  --------              --------
                                                                                                  $ 12,883              $ 11,029
                                                                                                  ========              ========



                                                                               8

                              MKS INSTRUMENTS, INC.
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS - (Continued)
                  (Tables in thousands, except per share data)


5)       Net Loss Per Share
         The following table sets forth the computation of basic and diluted net
         loss per share:



                                                                                                  Three Months Ended March 31,
                                                                                                   2002                   2001
                                                                                                   ----                   ----
                                                                                                                   
         Numerator
              Net loss...................................................................         $ (11,787)             $ (2,105)
                                                                                                  =========              ========
         Denominator
             Shares used in net loss per common share - basic and diluted................            46,288                36,820
                                                                                                  =========              ========
         Net loss per common share
             Basic and diluted...........................................................         $  (0.25)              $ (0.06)
                                                                                                  =========              ========


         For purposes of computing diluted earnings per share, weighted average
         common share equivalents do not include stock options with an exercise
         price greater than the average market price of the common shares during
         the period. All options outstanding during the three months ended March
         31, 2002 and 2001 are excluded from the calculation of diluted net
         income per common share because their inclusion would be anti-dilutive.
         There were options to purchase approximately 7,548,000 and 5,131,000
         shares of the Company's common stock outstanding as of March 31, 2002
         and 2001, respectively.

6)       Inventories
         Inventories consist of the following:



                                                                                                March 31,            December 31,
                                                                                                   2002                  2001
                                                                                                   ----                  ----
                                                                                                               
         Raw material....................................................................       $ 32,404               $ 21,019
         Work in process.................................................................         19,500                 15,362
         Finished goods..................................................................         27,200                 20,573
                                                                                                --------               --------
                                                                                                $ 79,104               $ 56,954
                                                                                                ========               ========


7)       Stockholders' Equity
         Total comprehensive loss was as follows:



                                                                                                 Three Months Ended March 31,
                                                                                                   2002                 2001
                                                                                                   ----                 ----
                                                                                                               
         Net loss........................................................................        $ (11,787)          $  (2,105)
         Other comprehensive loss, net of taxes:
             Changes in value of financial instruments designated
                  as hedges of currency and interest rate exposures......................             (156)                758
             Foreign currency translation adjustment.....................................             (340)               (606)
             Unrealized loss on investments..............................................              (55)               (313)
                                                                                                ----------           ---------
         Other comprehensive loss, net of taxes..........................................             (551)               (161)
                                                                                                ----------           ---------
         Total comprehensive loss........................................................       $  (12,338)          $  (2,266)
                                                                                                ==========           =========




                                                                               9

                              MKS INSTRUMENTS, INC.
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS - (Continued)
                  (Tables in thousands, except per share data)

8)       Segment Information and Significant Customer
         Segment information for the three months ended March 31, 2002 and 2001
         was as follows:



                                                                      North America       Far East         Europe          Total
                                                                                                               
                          Net sales to unaffiliated customers 2002        $39,394           $11,336         $8,337         $59,067
                                                              2001         81,132            17,363         12,393         110,888

                                       Intersegment net sales 2002         10,134               124            337          10,595
                                                              2001         18,392               330            392          19,114

                                Income (loss) from operations 2002        (17,197)              900          1,022         (15,275)
                                                              2001         (5,012)            1,885          2,446            (681)


         The Company had one customer comprising 16% and 23% of net sales for
         the three months ended March 31, 2002 and 2001, respectively.

9)       Commitments and Contingencies
         On November 3, 1999, On-Line Technologies Inc., which was acquired by
         the Company in April 2001, brought suit in federal district court in
         Connecticut against Perkin-Elmer, Inc. and certain other defendants for
         infringement of On-Line's patent related to its FTIR spectrometer
         product. The suit seeks injunctive relief and damages for infringement.
         Perkin-Elmer, Inc. has filed a counterclaim seeking invalidity of the
         patent, costs, and attorneys' fees. The Company believes that the
         counterclaim is without merit.

         On November 30, 2000, ASTeX, which was acquired by the Company in
         January 2001, brought suit in federal district court in Delaware
         against Advanced Energy Industries, Inc. for infringement of ASTeX's
         patent related to its Astron product. The Company is seeking injunctive
         relief and damages for infringement. Advanced Energy Industries, Inc.
         has filed a counterclaim seeking invalidity of the patent, costs, and
         attorneys' fees. The Company believes that the counterclaim is without
         merit.

         The Company cannot be certain of the outcome of the foregoing
         litigation, but does plan to assert its claims against other parties
         and oppose the counterclaims against it vigorously.

         The Company is subject to other legal proceedings and claims, which
         have arisen in the ordinary course of business.

         In the opinion of management, the ultimate disposition of these matters
         will not have a material adverse effect on the Company's results of
         operations, financial condition or cash flows.

10)      Acquisitions
         On January 31, 2002, MKS completed its acquisition of the ENI Business
         of Emerson Electric Co. ("ENI"), a supplier of solid-state radio
         frequency (RF) and direct current (DC) plasma power supplies, matching
         networks and instrumentation to the semiconductor thin-film processing
         industries. The reasons for the acquisition of ENI were based upon the
         ability to offer higher value and more integrated application solutions
         by combining ENI's solid-state power conversion technology with the
         Company's core competency in plasma and reactive gas solutions. The
         acquisition has been accounted for under the purchase method of
         accounting. The purchase price was approximately $266,310,000 and
         consisted of approximately 12,000,0000 shares of MKS common stock
         valued at approximately $261,264,000 and transaction expenses of
         approximately $5,046,000. The value of MKS common stock was
         approximately $21.7720 per share based on the average closing price of
         MKS' common stock for the five-day period including the date of the
         announcement of the signing of the merger agreement and the two days
         preceding and succeeding such date.


                                                                              10

                              MKS INSTRUMENTS, INC.
            NOTES TO CONSOLIDATED FINANCIAL STATEMENTS - (Continued)
                  (Tables in thousands, except per share data)

         The purchase price was allocated to the assets acquired based upon
         their estimated fair values and resulted in a preliminary allocation of
         approximately $203,496,000 to goodwill. The results of operations are
         included in the Company's consolidated statement of income as of and
         since the date of the purchase. The preliminary allocation of the
         purchase price was as follows:


                                                                              
         Current assets....................................................      $    31,090
         Other assets......................................................           21,564
         Intangibles subject to amortization...............................           34,600
         In-process research and development...............................            6,100
         Goodwill..........................................................          203,496
         Other liabilities.................................................          (10,801)
         Long term liabilities.............................................          (19,739)
                                                                                    --------
                                                                                    $266,310
                                                                                    ========


         The amounts allocated to acquired intangibles are being amortized using
         the straight-line method over their respective estimated useful lives,
         which range from 6 to 8 years.

         In connection with the acquisition of ENI, the Company obtained an
         appraisal from an independent appraiser of the fair value of its
         intangible assets. This appraisal valued purchased in-process research
         and development ("IPR&D") of various projects for the development of
         new products and technologies at approximately $6,100,000. Because the
         technological feasibility of products under development had not been
         established and no future alternative uses existed, the purchased IPR&D
         was written off during the quarter ended March 31, 2002. The value of
         the purchased IPR&D was determined using the income approach, which
         discounts expected future cash flows from projects under development to
         their net present value. Each project was analyzed to determine the
         technological innovations included; the utilization of core technology;
         the complexity, cost and time to complete development; any alternative
         future use or current technological feasibility; and the stage of
         completion. The cash flows derived from the IPR&D projects were
         discounted at rates ranging from 25% to 30%. The Company believes these
         rates were appropriate given the risks associated with the technologies
         for which commercial feasibility had not been established. The
         percentage of completion for each in-process project was determined by
         identifying the cost incurred to date of the project as a ratio of the
         total estimated cost required to bring the project to technical and
         commercial feasibility. The percentage of completion for in-process
         projects acquired ranged from 65% to 80%, based on management's
         estimates of tasks completed and the tasks to be completed to bring the
         projects to technological and commercial feasibility. The projects were
         generally expected to have durations of up to 12 months. As of March
         31, 2002, the actual development timelines and costs were in line with
         management's estimates.

         Development of in-process technology remains a substantial risk to the
         Company due to a variety of factors including the remaining effort to
         achieve technical feasibility, rapidly changing customer requirements
         and competitive threats from other companies and technologies.

         On March 13, 2002, MKS completed its acquisition of Tenta Technology
         Ltd. ("Tenta"), a supplier of modular, computer-based process control
         systems that are designed for 300mm semiconductor process tool
         applications. The reasons for the acquisition of Tenta were based upon
         the ability to offer higher value and more integrated application
         solutions by integrating Tenta's process controllers with MKS' digital
         network products to provide a more complete process control solution.
         The acquisition has been accounted for under the purchase method of
         accounting. The purchase price was allocated to the net assets acquired
         based upon their estimated fair values. The purchase price allocation
         is preliminary and dependent on the completion of the acquired
         intangibles valuation report. The results of operations are included in
         the Company's consolidated statement of income as of and since the date
         of the purchase.


                                                                              11

                              MKS INSTRUMENTS, INC.
                  NOTES TO CONSOLIDATED FINANCIAL STATEMENTS -
            (Continued) (Tables in thousands, except per share data)

         The following unaudited pro forma information presents a summary of the
         historical results of operations of the Company as if the ENI and Tenta
         acquisitions had occurred at the beginning of each period.



                                                                                                       Three months ended
                                                                                                           March 31,
                                                                                                   2002                  2001
                                                                                                   ----                  ----
                                                                                                                 
         Net sales.......................................................................          $ 63,207             $ 150,667
         Net income (loss)...............................................................          $ (7,087)            $   2,939

         Net income (loss) per share:
            Basic........................................................................          $ (0.14)              $  0.06
            Diluted......................................................................          $ (0.14)              $  0.06


         The unaudited pro forma results for the three months ended March 31,
         2002 excludes approximately $1.3 million of non-recurring charges
         directly related to the transaction that were incurred by Tenta prior
         to the date of the acquisition. Additionally, the charge for purchased
         IPR&D was not included in the unaudited pro forma results, because it
         was non-recurring and directly related to the transaction.

         These unaudited pro forma results have been prepared for comparative
         purposes only and do not purport to be indicative of the results of
         operations which actually would have resulted had the acquisition
         occurred at the beginning of the period, or which may result in the
         future.

11)      Subsequent Event
         On April 5, 2002, the Company completed its acquisition of privately
         held IPC Fab Automation GmbH, a developer and provider of web-based
         hardware and software that enable e-diagnostics and advanced process
         control for advanced manufacturing customers.


                                                                              12

                              MKS INSTRUMENTS, INC.
           MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION
                            AND RESULTS OF OPERATIONS

         ITEM 2.

This Quarterly Report on Form 10-Q contains "forward-looking statements" within
the meaning of the Private Securities Litigation Reform Act of 1995. When used
herein, including this Management's Discussion and Analysis, the words
"believes," "anticipates," "plans," "expects," and similar expressions are
intended to identify forward-looking statements. These forward-looking
statements reflect management's current opinions and are subject to certain
risks and uncertainties that could cause results to differ materially from those
stated or implied. MKS Instruments, Inc. assumes no obligation to update this
information. Risks and uncertainties include, but are not limited to, those
discussed in the section entitled "Factors That May Affect Future Results."

OVERVIEW

MKS develops, manufactures and supplies instruments, components and integrated
subsystems used to measure, control and monitor critical parameters of
semiconductor manufacturing and similar industrial manufacturing processes. The
Company estimates that during 2001 approximately 64% of its net sales were to
semiconductor capital equipment manufacturers and semiconductor device
manufacturers.

On January 31, 2002, MKS completed its acquisition of the ENI Business of
Emerson Electric Co. ("ENI"), a supplier of solid-state radio frequency (RF) and
direct current (DC) plasma power supplies, matching networks and instrumentation
to the semiconductor thin-film processing industries. The reasons for the
acquisition of ENI were based upon the ability to offer higher value and more
integrated application solutions by combining ENI's solid-state power conversion
technology with the Company's core competency in plasma and reactive gas
solutions. The acquisition has been accounted for under the purchase method of
accounting. The purchase price was approximately $266,310,000 and consisted of
approximately 12,000,0000 shares of MKS common stock valued at approximately
$261,264,000 and transaction expenses of approximately $5,046,000. The value of
MKS common stock was approximately $21.7720 per share based on the average
closing price of MKS' common stock for the five-day period including the date of
the announcement of the signing of the merger agreement and the two days
preceding and succeeding such date. The purchase price was allocated to the
assets acquired based upon their estimated fair values and resulted in a
preliminary allocation of approximately $203,496,000 to goodwill. The results of
operations are included in the Company's consolidated statement of income as of
and since the date of the purchase.



                                                                              13

RESULTS OF OPERATIONS

The following table sets forth for the periods indicated the percentage of total
net sales of certain line items included in MKS' consolidated statement of
income data.



                                                                   Three months ended
                                                                        March 31,
                                                                  2002             2001
                                                                  ----             ----

                                                                            
Net sales .............................................          100.0%           100.0%
Cost of sales .........................................           67.5             61.0
                                                                 -----            -----
Gross profit ..........................................           32.5             39.0
Research and development ..............................           15.5             10.1
Selling, general and administrative ...................           28.9             17.2
Amortization of goodwill and acquired intangible assets            3.7              2.0
Goodwill impairment charge ............................             --              3.4
Merger expenses .......................................             --              6.9
In-process research and development ...................           10.3               --
                                                                 -----            -----
Loss from operations ..................................          (25.9)            (0.6)
Interest income, net ..................................            0.7              1.2
                                                                 -----            -----
Income (loss) before income taxes .....................          (25.2)             0.6
Provision (benefit) for income taxes ..................           (5.2)             2.5
                                                                 -----            -----
Net loss ..............................................          (20.0)%           (1.9)%
                                                                 =====            =====


         Net Sales. Net sales decreased 46.7% to $59.1 million for the three
months ended March 31, 2002 from $110.9 million for the three months ended March
31, 2001. International net sales were approximately $19.7 million for the three
months ended March 31, 2002 or 33.3% of net sales and $29.8 million for the same
period of 2001 or 26.8% of net sales. The decrease in net sales is due to a
worldwide slowdown in demand for semiconductors during 2001 and continuing
through the first quarter of 2002, which resulted in a decline in demand for the
Company's products from the Company's semiconductor capital equipment
manufacturers and semiconductor device manufacturer customers.

         Gross Profit. Gross profit as a percentage of net sales decreased to
32.5% for the three months ended March 31, 2002 from 39.0% for the three months
ended March 31, 2001. The decrease was primarily due to lower absorption of
manufacturing overhead costs.

         Research and Development. Research and development expense decreased
18.1% to $9.1 million or 15.5% of net sales for the three months ended March 31,
2002 from $11.2 million or 10.1% of net sales for the three months ended March
31, 2001. The decrease was primarily due to decreased compensation expense of
$1.2 million and decreased expenses for project materials related to projects in
process of $0.6 million.

         Selling, General and Administrative. Selling, general and
administrative expenses decreased 10.5% to $17.1 million or 28.9% of net sales
for the three months ended March 31, 2002 from $19.1 million or 17.2% of net
sales for the three months ended March 31, 2001. The decrease was due primarily
to decreased compensation expense of $1.2 million and decreased purchased
services of $0.4 million.

         Amortization of Goodwill and Acquired Intangible Assets. Amortization
expense of $2.2 million for the three months ended March 31, 2002 represents the
amortization of the identifiable intangibles resulting from the acquisitions
completed by MKS. In accordance with SFAS No. 142, the Company ceased to
amortize goodwill on January 1, 2002. Amortization of goodwill was $1.1 million
and amortization of the identifiable intangibles was $1.1 million for the three
months ended March 31, 2001.


                                                                              14

         Purchase of In-process Technology. In January 2002, the Company
acquired ENI in a transaction accounted for as a purchase. The purchase price
was allocated to the assets acquired, including intangible assets, based on
their estimated fair values. The intangible assets include approximately $6.1
million for acquired in-process technology for projects, generally expected to
have durations of 12 months, that did not have future alternative uses. The
value of the purchased in-process technology was determined using the income
approach, which discounts expected future cash flows from projects under
development to their net present value. Each project was analyzed to determine
the technological innovations included; the utilization of core technology; the
complexity, cost and time to complete development; any alternative future use or
current technological feasibility; and the stage of completion. The cash flows
derived from the in-process technology projects were discounted at rates ranging
from 25% to 30%. The Company believes these rates were appropriate given the
risks associated with the technologies for which commercial feasibility had not
been established. The percentage of completion for each in-process project was
determined by identifying the cost incurred to date of the project as a ratio of
the total cost required to bring the project to technical and commercial
feasibility. The percentage completion for in-process projects acquired ranged
from 65% to 80% complete, based on management's estimates of tasks completed and
the tasks to be completed to bring the projects to technological and commercial
feasibility. At the date of the acquisition, the development of these projects
had not yet reached technological feasibility, and the technology in progress
had no alternative future uses. Accordingly, these costs were expensed in the
first quarter of 2002.

         Interest Income (Expense), Net. During the three months ended March 31,
2002, the Company generated net interest income of $0.4 million primarily from
the invested net proceeds of its common stock offerings, offset by interest
expense on outstanding debt.

         Provision (Benefit) for Income Taxes. The effective tax rates for the
three months ended March 31, 2002 and 2001 were 20.6% and 396.1%, respectively,
resulting in a benefit for income taxes of $3.1 million and provision for income
taxes of $2.8 million, respectively. The effective tax rates for the three
months ended March 31, 2002 and 2001 differed from the statutory rate of 35% due
primarily to non-deductible charges associated with acquisitions made in 2002
and 2001.

LIQUIDITY AND CAPITAL RESOURCES

The Company has financed its operations and capital requirements through a
combination of cash provided by operations, long-term real estate financing,
capital lease financing and short-term lines of credit.

Operations used cash of $2.8 million for the three months ended March 31, 2002.
The cash flow from operations in the first quarter of 2002 was impacted by the
net loss of $11.8, increases in accounts receivable and inventories of $10.3
million and $1.8 million, respectively, and offset by non-cash charges for
in-process research and development of $6.1 million, depreciation and
amortization of $5.6 million, and an increase in accounts payable of $3.3
million. Investing activities utilized cash of $24.1 million for the three
months ended March 31, 2002 primarily from purchases of investments. Financing
activities provided cash of $3.3 million, primarily from proceeds from employees
exercising stock options.

Working capital was $224.1 million as of March 31, 2002, an increase of $7.2
million from December 31, 2001. The increase in working capital was primarily
due to increased trade accounts receivable. MKS entered into a credit agreement
on July 31, 2001 whereby the Company has a combined $40.0 million line of credit
with two banks. The credit agreement expires on July 31, 2002. The line of
credit is collateralized by the Company's domestic accounts receivable and
domestic inventory for borrowings exceeding $5.0 million. There were no
borrowings under this line of credit as of March 31, 2002.

The Company believes that its working capital, together with the cash
anticipated to be generated from operations and funds available from existing
credit facilities, will be sufficient to satisfy its estimated working capital
and planned capital expenditure requirements through at least the next 12
months.



                                                                              15

                     FACTORS THAT MAY AFFECT FUTURE RESULTS

MKS believes that this document contains "forward-looking statements" within the
meaning of the Private Securities Litigation Reform Act of 1995. These
statements are subject to risks and uncertainties and are based on the beliefs
and assumptions of management of MKS, based on information currently available
to MKS' management. Use of words such as "believes," "expects," "anticipates,"
"intends," "plans," "estimates," "should," "likely" or similar expressions,
indicate a forward-looking statement. Forward-looking statements involve risks,
uncertainties and assumptions. Certain of the information contained in this
Quarterly Report on Form 10-Q consists of forward-looking statements. Important
factors that could cause actual results to differ materially from the
forward-looking statements include the following:

MKS' BUSINESS DEPENDS SUBSTANTIALLY ON CAPITAL SPENDING IN THE SEMICONDUCTOR
INDUSTRY WHICH IS CHARACTERIZED BY PERIODIC FLUCTUATIONS THAT MAY CAUSE A
REDUCTION IN DEMAND FOR MKS' PRODUCTS.

MKS estimates that approximately 64% of its sales during 2001 were to
semiconductor capital equipment manufacturers and semiconductor device
manufacturers, and it expects that sales to such customers will continue to
account for a substantial majority of its sales. MKS' business depends upon the
capital expenditures of semiconductor device manufacturers, which in turn depend
upon the demand for semiconductors. Periodic reductions in demand for the
products manufactured by semiconductor capital equipment manufacturers and
semiconductor device manufacturers may adversely affect MKS' business, financial
condition and results of operations. Historically, the semiconductor market has
been highly cyclical and has experienced periods of overcapacity, resulting in
significantly reduced demand for capital equipment. For example, in 1996 and
1998, the semiconductor capital equipment industry experienced significant
declines, which caused a number of MKS' customers to reduce their orders. More
recently, in 2001 and continuing through the first quarter of 2002, MKS
experienced a significant reduction in demand from OEM customers, and lower
gross margins due to reduced absorption of manufacturing overhead at the lower
revenue levels. MKS incurred special charges for excess and obsolete inventory
of $14.0 million in the fourth quarter of 2001 and $2.6 million in the second
quarter of 2001. The charges were significantly higher than normal and were
primarily caused by a significant reduction in demand including reduced demand
for older technology products. In addition, many semiconductor manufacturers
have operations and customers in Asia, a region which in recent years has
experienced serious economic problems including currency devaluations, debt
defaults, lack of liquidity and recessions. MKS cannot be certain that
semiconductor downturns will not recur. A decline in the level of orders as a
result of any future downturn or slowdown in the semiconductor capital equipment
industry could have a material adverse effect on MKS' business, financial
condition and results of operations.

MKS' QUARTERLY OPERATING RESULTS HAVE VARIED, AND ARE LIKELY TO CONTINUE TO VARY
SIGNIFICANTLY. THIS MAY RESULT IN VOLATILITY IN THE MARKET PRICE FOR MKS'
SHARES.

A substantial portion of MKS' shipments occur shortly after an order is received
and therefore MKS operates with a low level of backlog. As a result, a decrease
in demand for MKS' products from one or more customers could occur with limited
advance notice and could have a material adverse effect on MKS' results of
operations in any particular period. A significant percentage of MKS' expenses
are relatively fixed and based in part on expectations of future net sales. The
inability to adjust spending quickly enough to compensate for any shortfall
would magnify the adverse impact of a shortfall in net sales on MKS' results of
operations. Factors that could cause fluctuations in MKS' net sales include:

- -        the timing of the receipt of orders from major customers;
- -        shipment delays;
- -        disruption in sources of supply;
- -        seasonal variations of capital spending by customers;
- -        production capacity constraints; and
- -        specific features requested by customers.


                                                                              16

For example, MKS was in the process of increasing its production capacity when
the semiconductor capital equipment market began to experience a significant
downturn in 1996. This downturn had a material adverse effect on MKS' operating
results in the second half of 1996 and the first half of 1997. After an increase
in business in the latter half of 1997, the market experienced another downturn
in 1998, which had a material adverse effect on MKS' 1998 and first quarter 1999
operating results. More recently, the semiconductor capital equipment market
experienced a significant downturn during 2001 and continuing through the first
quarter of 2002. As a result, MKS experienced a reduction in demand from OEM
customers in 2001 and the first quarter of 2002, which has had a material
adverse effect on MKS' operating results. During 2001 gross margins were
negatively affected by special charges for excess and obsolete inventory of
$14.0 million in the fourth quarter of 2001 and $2.6 million in the second
quarter of 2001. The charges were significantly higher than normal and were
primarily caused by a significant reduction in demand including reduced demand
for older technology products. As a result of the factors discussed above, it is
likely that MKS will in the future experience quarterly or annual fluctuations
and that, in one or more future quarters, its operating results will fall below
the expectations of public market analysts or investors. In any such event, the
price of MKS' common stock could decline significantly.

THE LOSS OF NET SALES TO ANY ONE OF MKS' MAJOR CUSTOMERS WOULD LIKELY HAVE A
MATERIAL ADVERSE EFFECT ON MKS.

MKS' top ten customers accounted for approximately 39% of its net sales in 2001,
52% of its net sales in 2000 and 46% of its net sales in 1999. The loss of a
major customer or any reduction in orders by these customers, including
reductions due to market or competitive conditions, would likely have a material
adverse effect on MKS' business, financial condition and results of operations.
During 2001 and 2000, one customer, Applied Materials, accounted for
approximately 18% and 30%, respectively, of MKS' net sales. None of MKS'
significant customers, including Applied Materials, has entered into an
agreement requiring it to purchase any minimum quantity of MKS' products. The
demand for MKS' products from its semiconductor capital equipment customers
depends in part on orders received by them from their semiconductor device
manufacturer customers.

Attempts to lessen the adverse effect of any loss or reduction through the rapid
addition of new customers could be difficult because prospective customers
typically require lengthy qualification periods prior to placing volume orders
with a new supplier. MKS' future success will continue to depend upon:

- -        its ability to maintain relationships with existing key customers;
- -        its ability to attract new customers; and
- -        the success of its customers in creating demand for their capital
         equipment products which incorporate MKS' products.

AS PART OF MKS' BUSINESS STRATEGY, MKS HAS ENTERED INTO AND MAY ENTER INTO OR
SEEK TO ENTER INTO BUSINESS COMBINATIONS AND ACQUISITIONS THAT MAY BE DIFFICULT
TO INTEGRATE, DISRUPT ITS BUSINESS, DILUTE STOCKHOLDER VALUE OR DIVERT
MANAGEMENT ATTENTION.

MKS acquired Compact Instrument Technology, LLC ("Compact Instrument") in March
2000, Telvac Engineering, Ltd. ("Telvac") in May 2000, Spectra Instruments, LLC
("Spectra") in July 2000, D.I.P., Inc. ("D.I.P.") in September 2000, Applied
Science and Technology, Inc. ("ASTeX") in January 2001, On-Line Technologies,
Inc. ("On-Line") in April 2001, the ENI Business ("ENI") of Emerson Electric Co.
in January 2002, Tenta Technologies Ltd. ("Tenta") in March 2002, and IPC Fab
Automation GmbH ("IPC") in April 2002. As a part of its business strategy, MKS
may enter into additional business combinations and acquisitions. Acquisitions
are typically accompanied by a number of risks, including the difficulty of
integrating the operations and personnel of the acquired companies, the
potential disruption of MKS' ongoing business and distraction of management,
expenses related to the acquisition and potential unknown liabilities associated
with acquired businesses.

If MKS is not successful in completing acquisitions that it may pursue in the
future, it may be required to reevaluate its growth strategy, and MKS may have
incurred substantial expenses and devoted significant management time and
resources in seeking to complete proposed acquisitions that will not generate
benefits for it.


                                                                              17

In addition, with future acquisitions, MKS could use substantial portions of its
available cash as all or a portion of the purchase price. MKS could also issue
additional securities as consideration for these acquisitions, which could cause
significant stockholder dilution. MKS' acquisitions of Compact Instrument,
Telvac, Spectra, D.I.P., ASTeX, On-Line, ENI, Tenta, and IPC and any future
acquisitions may not ultimately help MKS achieve its strategic goals and may
pose other risks to MKS.

AN INABILITY TO CONVINCE SEMICONDUCTOR DEVICE MANUFACTURERS TO SPECIFY THE USE
OF MKS' PRODUCTS TO MKS' CUSTOMERS, WHO ARE SEMICONDUCTOR CAPITAL EQUIPMENT
MANUFACTURERS, WOULD WEAKEN MKS' COMPETITIVE POSITION.

The markets for MKS' products are highly competitive. Its competitive success
often depends upon factors outside of its control. For example, in some cases,
particularly with respect to mass flow controllers, semiconductor device
manufacturers may direct semiconductor capital equipment manufacturers to use a
specified supplier's product in their equipment. Accordingly, for such products,
MKS' success will depend in part on its ability to have semiconductor device
manufacturers specify that MKS' products be used at their semiconductor
fabrication facilities. In addition, MKS may encounter difficulties in changing
established relationships of competitors that already have a large installed
base of products within such semiconductor fabrication facilities.

IF MKS' PRODUCTS ARE NOT DESIGNED INTO SUCCESSIVE NEW GENERATIONS OF ITS
CUSTOMERS' PRODUCTS, MKS WILL LOSE SIGNIFICANT NET SALES DURING THE LIFESPAN OF
THOSE PRODUCTS.

New products designed by semiconductor capital equipment manufacturers typically
have a lifespan of five to ten years. MKS' success depends on its products being
designed into new generations of equipment for the semiconductor industry. MKS
must develop products that are technologically current so that they are
positioned to be chosen for use in each successive new generation of
semiconductor capital equipment. If MKS products are not chosen by its
customers, MKS' net sales may be reduced during the lifespan of its customers'
products. In addition, MKS must make a significant capital investment to develop
products for its customers well before its products are introduced and before it
can be sure that it will recover its capital investment through sales to the
customers in significant volume. MKS is thus also at risk during the development
phase that its products may fail to meet its customers' technical or cost
requirements and may be replaced by a competitive product or alternative
technology solution. If that happens, MKS may be unable to recover MKS'
development costs.

THE SEMICONDUCTOR INDUSTRY IS SUBJECT TO RAPID DEMAND SHIFTS WHICH ARE DIFFICULT
TO PREDICT. AS A RESULT, MKS' INABILITY TO EXPAND ITS MANUFACTURING CAPACITY IN
RESPONSE TO THESE RAPID SHIFTS MAY CAUSE A REDUCTION IN ITS MARKET SHARE.

MKS' ability to increase sales of certain products depends in part upon its
ability to expand its manufacturing capacity for such products in a timely
manner. If MKS is unable to expand its manufacturing capacity on a timely basis
or to manage such expansion effectively, its customers could implement its
competitors' products and, as a result, its market share could be reduced.
Because the semiconductor industry is subject to rapid demand shifts which are
difficult to foresee, MKS may not be able to increase capacity quickly enough to
respond to a rapid increase in demand in the semiconductor industry.
Additionally, capacity expansion could increase MKS' fixed operating expenses
and if sales levels do not increase to offset the additional expense levels
associated with any such expansion, its business, financial condition and
results of operations could be materially adversely affected.

SALES TO FOREIGN MARKETS CONSTITUTE A SUBSTANTIAL PORTION OF MKS' NET SALES;
THEREFORE, MKS NET SALES AND RESULTS OF OPERATIONS COULD BE ADVERSELY AFFECTED
BY DOWNTURNS IN ECONOMIC CONDITIONS IN COUNTRIES OUTSIDE OF THE UNITED STATES.

International sales, which include sales by MKS' foreign subsidiaries, but
exclude direct export sales (which were less than 10% of MKS' total net sales),
accounted for approximately 31% of net sales in 2001, 23% of net sales in 2000
and 25% of net sales in 1999.



                                                                              18

MKS anticipates that international sales will continue to account for a
significant portion of MKS' net sales. In addition, certain of MKS' key domestic
customers derive a significant portion of their revenues from sales in
international markets. Therefore, MKS' sales and results of operations could be
adversely affected by economic slowdowns and other risks associated with
international sales.

RISKS RELATING TO MKS' INTERNATIONAL OPERATIONS COULD ADVERSELY AFFECT MKS'
OPERATING RESULTS.

MKS has substantial international sales, service, and manufacturing operations
in Europe and Asia, which exposes MKS to foreign operational and political
risks that may harm MKS' business. MKS' international operations are subject to
inherent risks, which may adversely affect MKS, including:

- -        political and economic instability in countries where we have sales,
         service, and manufacturing operations, particularly in Asia;
- -        fluctuations in the value of currencies and high levels of inflation,
         particularly in Asia;
- -        changes in labor conditions and difficulties in staffing and managing
         foreign operations, including, but not limited to, labor unions;
- -        greater difficulty in collecting accounts receivable and longer payment
         cycles;
- -        burdens and costs of compliance with a variety of foreign laws;
         increases in duties and taxation;
- -        imposition of restrictions on currency conversion or the transfer of
         funds;
- -        changes in export duties and limitations on imports or exports;
- -        expropriation of private enterprises; and
- -        unexpected changes in foreign regulations.

If any of these risks materialize, our operating results may be adversely
affected.

UNFAVORABLE CURRENCY EXCHANGE RATE FLUCTUATIONS MAY LEAD TO LOWER GROSS MARGINS,
OR MAY CAUSE MKS TO RAISE PRICES WHICH COULD RESULT IN REDUCED SALES.

Currency exchange rate fluctuations could have an adverse effect on MKS' net
sales and results of operations and MKS could experience losses with respect to
its hedging activities. Unfavorable currency fluctuations could require MKS to
increase prices to foreign customers which could result in lower net sales by
MKS to such customers. Alternatively, if MKS does not adjust the prices for its
products in response to unfavorable currency fluctuations, its results of
operations could be adversely affected. In addition, sales made by MKS' foreign
subsidiaries are denominated in the currency of the country in which these
products are sold and the currency it receives in payment for such sales could
be less valuable at the time of receipt as a result of exchange rate
fluctuations. MKS enters into forward exchange contracts and local currency
purchased options to reduce currency exposure arising from intercompany sales of
inventory. However, MKS cannot be certain that its efforts will be adequate to
protect it against significant currency fluctuations or that such efforts will
not expose it to additional exchange rate risks.

KEY PERSONNEL MAY BE DIFFICULT TO ATTRACT AND RETAIN.

MKS' success depends to a large extent upon the efforts and abilities of a
number of key employees and officers, particularly those with expertise in the
semiconductor manufacturing and similar industrial manufacturing industries. The
loss of key employees or officers could have a material adverse effect on MKS'
business, financial condition and results of operations. MKS believes that its
future success will depend in part on its ability to attract and retain highly
skilled technical, financial, managerial and marketing personnel. MKS cannot be
certain that it will be successful in attracting and retaining such personnel.


                                                                              19

MKS' PROPRIETARY TECHNOLOGY IS IMPORTANT TO THE CONTINUED SUCCESS OF ITS
BUSINESS. MKS' FAILURE TO PROTECT THIS PROPRIETARY TECHNOLOGY MAY SIGNIFICANTLY
IMPAIR MKS' COMPETITIVE POSITION.

As of March 31, 2002, MKS owned 125 U.S. patents and 84 foreign patents and had
59 pending U.S. patent applications and 137 pending foreign patent applications.
Although MKS seeks to protect its intellectual property rights through patents,
copyrights, trade secrets and other measures, it cannot be certain that:


- -        MKS will be able to protect its technology adequately;
- -        competitors will not be able to develop similar technology
         independently;
- -        any of MKS' pending patent applications will be issued;
- -        intellectual property laws will protect MKS' intellectual property
         rights; or
- -        third parties will not assert that MKS' products infringe patent,
         copyright or trade secrets of such parties.

PROTECTION OF MKS' INTELLECTUAL PROPERTY RIGHTS MAY RESULT IN COSTLY LITIGATION.

Litigation may be necessary in order to enforce MKS' patents, copyrights or
other intellectual property rights, to protect its trade secrets, to determine
the validity and scope of the proprietary rights of others or to defend against
claims of infringement. For example, on November 30, 2000, MKS' ASTeX subsidiary
brought suit in federal district court in Delaware against Advanced Energy
Industries, Inc. for infringement of ASTeX's patent related to its Astron
product. Such litigation could result in substantial costs and diversion of
resources and could have a material adverse effect on MKS' business, financial
condition and results of operations.

THE MARKET PRICE OF MKS' COMMON STOCK HAS FLUCTUATED AND MAY CONTINUE TO
FLUCTUATE FOR REASONS OVER WHICH MKS HAS NO CONTROL.

The stock market has from time to time experienced, and is likely to continue to
experience, extreme price and volume fluctuations. Recently, prices of
securities of technology companies have been especially volatile and have often
fluctuated for reasons that are unrelated to the operating performance of the
companies. The market price of shares of MKS' common stock has fluctuated
greatly since its initial public offering and could continue to fluctuate due to
a variety of factors. In the past, companies that have experienced volatility in
the market price of their stock have been the objects of securities class action
litigation. If MKS were the object of securities class action litigation, it
could result in substantial costs and a diversion of MKS' management's attention
and resources.

MKS' DEPENDENCE ON SOLE AND LIMITED SOURCE SUPPLIERS COULD AFFECT ITS ABILITY TO
MANUFACTURE PRODUCTS AND SYSTEMS.

MKS relies on sole and limited source suppliers for a few of its components and
subassemblies that are critical to the manufacturing of MKS' products. This
reliance involves several risks, including the following:

- -        the potential inability to obtain an adequate supply of required
         components;
- -        reduced control over pricing and timing of delivery of components; and
- -        the potential inability of its suppliers to develop technologically
         advanced products to support MKS' growth and development of new
         systems.

MKS believes that in time MKS could obtain and qualify alternative sources for
most sole and limited source parts. Seeking alternative sources of the parts
could require MKS to redesign its systems, resulting in increased costs and
likely shipping delays. MKS may be unable to redesign its systems, which could
result in further costs and shipping delays. These increased costs would
decrease MKS' profit margins if it could not pass the costs to its customers.
Further, shipping delays could damage MKS' relationships with current and
potential customers and have a material adverse effect on MKS' business and
results of operations.


                                                                              20

MKS IS SUBJECT TO GOVERNMENTAL REGULATIONS.

MKS is subject to federal, state, local and foreign regulations, including
environmental regulations and regulations relating to the design and operation
of MKS' power supply products. MKS must ensure that these systems meet certain
safety standards, many of which vary across the countries in which MKS' systems
are used. For example, the European Union has published directives specifically
relating to power supplies. MKS must comply with these directives in order to
ship MKS' systems into countries that are members of the European Union. MKS
believes it is in compliance with current applicable regulations, directives and
standards and has obtained all necessary permits, approvals, and authorizations
to conduct MKS' business. However, compliance with future regulations,
directives and standards could require it to modify or redesign certain systems,
make capital expenditures or incur substantial costs. If MKS does not comply
with current or future regulations, directives and standards:

- -        MKS could be subject to fines;
- -        MKS' production could be suspended; or
- -        MKS could be prohibited from offering particular systems in specified
         markets.

CERTAIN STOCKHOLDERS HAVE A SUBSTANTIAL INTEREST IN MKS AND MAY BE ABLE TO EXERT
SUBSTANTIAL INFLUENCE OVER MKS' ACTIONS.

As of January 31, 2002, John R. Bertucci, president, chairman and chief
executive officer of MKS, and certain members of his family, in the aggregate,
beneficially owned approximately 29.8% of MKS' outstanding common stock. As a
result, these stockholders, acting together, are able to exert substantial
influence over the actions of MKS. Pursuant to the acquisition of the ENI
Business of Emerson Electric Co. ("Emerson"), MKS issued approximately 24% of
its then outstanding shares of common stock to Emerson. Accordingly, Emerson is
able to exert substantial influence over MKS' actions.

SOME PROVISIONS OF MKS' RESTATED ARTICLES OF ORGANIZATION, AS AMENDED, MKS'
AMENDED AND RESTATED BY-LAWS AND MASSACHUSETTS LAW COULD DISCOURAGE POTENTIAL
ACQUISITION PROPOSALS AND COULD DELAY OR PREVENT A CHANGE IN CONTROL OF MKS.

Anti-takeover provisions could diminish the opportunities for stockholders to
participate in tender offers, including tender offers at a price above the then
current market value of the common stock. Such provisions may also inhibit
increases in the market price of the common stock that could result from
takeover attempts. For example, while MKS has no present plans to issue any
preferred stock, MKS' board of directors, without further stockholder approval,
may issue preferred stock that could have the effect of delaying, deterring or
preventing a change in control of MKS. The issuance of preferred stock could
adversely affect the voting power of the holders of MKS' common stock, including
the loss of voting control to others. In addition, MKS' amended and restated
by-laws provide for a classified board of directors consisting of three classes.
The classified board could also have the effect of delaying, deterring or
preventing a change in control of MKS.


                                                                              21

         ITEM 3.  QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

Information concerning market risk is contained in the Management's Discussion
and Analysis of Financial Condition and Results of Operations contained in the
Consolidated Financial Statements for year ended December 31, 2001, which was
filed on Form 10-K on April 1, 2002. MKS enters into local currency purchased
options and forward exchange contracts to reduce currency exposure arising from
intercompany sales of inventory. The potential fair value loss for a
hypothetical 10% adverse change in currency exchange rates on MKS' local
currency purchased options at March 31, 2002 would be approximately $ 300,000.
The potential loss was estimated by calculating the fair value of the local
currency purchased options at March 31, 2002 and comparing that with those
calculated using the hypothetical currency exchange rates. The potential fair
value loss for a hypothetical 10% adverse change in the forward currency
exchange rate on MKS' forward exchange contracts at March 31, 2002 would be
$458,000. The potential loss was estimated by calculation the fair value of the
forward exchange contacts at March 31, 2002 and comparing that with those
calculated using the hypothetical forward currency exchange rate. There were no
other material changes in MKS' exposure to market risk from December 31, 2001.

PART II  OTHER INFORMATION

         ITEM 1.  LEGAL PROCEEDINGS

There have been no material developments since the filing of MKS' Annual Report
on Form 10-K on April 1, 2002.

         ITEM 2.  CHANGES IN SECURITIES AND USE OF PROCEEDS

(c)      Recent Sales of Unregistered Securities.

                  On January 31, 2002, MKS issued 12,000,000 shares of its
         common stock to Emerson Electric Co., the former stockholder of the ENI
         Business, in connection with its acquisition of the ENI Business. The
         shares of common stock were exempt from registration under Section 4(2)
         of the Securities Act of 1933, as amended, because there was no public
         offering of the common stock issued. No underwriters were involved in
         the sale of these securities.

                  On March 13, 2002, MKS issued an aggregate of 700,000 shares
         of its common stock to the former stockholders of Tenta Technology
         Ltd. ("Tenta") in connection with its acquisition of Tenta. Of the
         700,000 shares issued, 337,780 shares of common stock were exempt from
         registration under Regulation D of the Securities Act of 1933, as
         amended and 362,220 shares of common stock were exempt from
         registration under Regulation S of the Securities Act of 1933, as
         amended. No underwriters were involved in the sale of these securities.

         (d) Use of Proceeds from Sales of Registered Securities. The Company
         has previously provided information on Form 10-Q for the quarter ended
         September 30, 2000 relating to the use of proceeds from the sale of
         securities by the Company pursuant to the Registration Statement on
         Form S-1 (Reg. No. 333-71363) that was declared effective by the
         Securities and Exchange Commission on March 29, 1999. As of March 31,
         2002, approximately $20.8 million of the net proceeds from the
         securities sold has been used to acquire businesses. There has been no
         other change to the information previously provided.

         ITEM 3.  DEFAULTS UPON SENIOR SECURITIES

None.

         ITEM 4.  SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

None.

         ITEM 5.  OTHER INFORMATION

None.


                                                                              22

         ITEM 6.  EXHIBITS AND REPORTS ON FORM 8-K


(a)      Exhibits

         Exhibit No.       Exhibit Description

         10.1.1            Fourth Amendment to Amended and Restated 1995 Stock
                           Incentive Plan of MKS Instruments, Inc.
         10.1.2            Fifth Amendment to Amended and Restated 1995 Stock
                           Incentive Plan of MKS, Inc.


(b)      Reports on Form 8-K

                  The Company filed a Current Report on Form 8-K on February 12,
         2002 and Amendment No. 1 to such Current Report on Form 8-K on April
         15, 2002 to report that the Company had completed its acquisition of
         the ENI Business of Emerson Electric Co. and to provide the financial
         statements and the pro forma financial information required.



                                                                              23

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

                                    MKS INSTRUMENTS, INC.




May 15, 2002                    By:  /s/ Ronald C. Weigner
                                     Ronald C. Weigner
                                     Vice President and Chief Financial Officer
                                     (Principal Financial Officer)






                                                                              24

EXHIBIT INDEX




         Exhibit No.       Exhibit Description
               10.1.1      Fourth Amendment to Amended and Restated 1995 Stock
                           Incentive Plan of MKS Instruments, Inc.

               10.1.2      Fifth Amendment to Amended and Restated 1995 Stock
                           Incentive Plan of MKS, Inc.




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