EXHIBIT 99.2

                    CERTIFICATION OF CHIEF FINANCIAL OFFICER

                       PURSUANT TO 18 U.S.C. SECTION 1350,

                             AS ADOPTED PURSUANT TO

                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002


       In connection with the Annual Report on Form 10-K of MKS Instruments,
Inc. (the "Company") for the period ended December 31, 2002 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), the
undersigned, Ronald C. Weigner, Vice President and Chief Financial Officer of
the Company, hereby certifies, pursuant to 18 U.S.C. Section 1350, that:

         (1) the Report fully complies with the requirements of Section 13(a) or
15(d) of the Securities Exchange Act of 1934; and

         (2) the information contained in the Report fairly presents, in all
material respects, the financial condition and results of operations of the
Company.

Dated: March 31, 2003
                                    /s/ Ronald C. Weigner
                                    ------------------------------------------
                                    Ronald C. Weigner
                                    Vice President and Chief Financial Officer



A signed original of this written statement required by Section 906 has been
provided to MKS Instruments, Inc. and will be retained by MKS Instruments, Inc.
and furnished to the Securities and Exchange Commission or its staff upon
request.