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                       [MKS INSTRUMENTS, INC. LETTERHEAD]

November 18, 1998

VIA EDGAR

Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C. 20549
Attention:  Ms. Goldie Walker


Re:      MKS Instruments, Inc. Form S-1 (File No. 333-40269)

Ladies and Gentlemen:

MKS Instruments, Inc., a Massachusetts corporation (the "Company"), pursuant to
Rule 477(a) promulgated under the Securities Act of 1933, as amended, hereby
requests that the Securities and Exchange Commission consent to the withdrawal
of the Company's Registration Statement on Form S-1 (File No. 333-40269),
together with all amendments and exhibits thereto. The Company requests
withdrawal of the Registration Statement because it does not intend to conduct
the offering of shares of Common Stock contemplated in the Registration
Statement at this time. No shares of Common Stock of the Company have been
issued or sold under the Registration.

The Company further requests that, pursuant to Rule 477(c), an order with the
date of granting of the withdrawal be included in the file for the Registration
Statement on Form S-1 in the following manner: "Withdrawn upon the request of
the Registrant, the Commission consenting thereto."

If you have any questions or comments or require further information or
documentation, please do not hesitate to call the undersigned at (978) 975-2350
or Richard N. Kimball, Esq. at (617) 526-6658.

Sincerely,

/S/ John R. Bertucci

John R. Bertucci
Chairman of the Board, President and Chief Executive Officer


cc:  Richard N. Kimball, Esq.