MKS INC — Director's Dealing 2012

May 30, 2012

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2012-05-29

Reporting Person: Loomis Paul (VP & GM, Astex)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2012-05-29	Common Stock	M	4000	—	Acquired	5394	Direct
2012-05-29	Common Stock	F	1268	$26.43	Disposed	4126	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2012-05-29	Restricted Stock Unit	$	M	4000	Disposed		Common Stock (4000)	Direct

Footnotes

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

F2: This transaction was effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person.

F3: The RSUs vest three years after grant date.