MKS INC — Director's Dealing 2010

Mar 3, 2010

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2010-03-01

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

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-03-01	Common Stock	M	3787	—	Acquired	3787	Direct
2010-03-01	Common Stock	F	1396	$18.35	Disposed	2391	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-03-01	Restricted Stock Unit	$	M	3787	Disposed		Common Stock (3787)	Direct

Footnotes

F1: This transaction was effected pursuant to a Rule 10b5-1 plan previously adopted by the reporting person to satisfy tax withholding obligation.

F2: Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc.

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