MKS INC — Director's Dealing 2010

Mar 8, 2010

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2010-03-04

Reporting Person: STEWART WILLIAM D (V.P. Vacuum Products & PFMC)

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-03-04	Restricted Stock Unit	$	A	8400	Acquired		Common Stock (8400)	Direct
2010-03-04	Restricted Stock Unit	$	A	6000	Acquired		Common Stock (6000)	Direct

Footnotes

F1: Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc.

F2: These RSUs are subject to the achievement of performance criteria determined in the first year of the grant and thereafter vests in equal annual installments over three years.

F3: The RSUs vest in equal annual installments over three years.