MKS INC - Director's Dealing 2011

SEC Form 5 — Annual Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2010-12-31

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

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-07-01	Common Stock	M	3000	—	Acquired	4388	Direct
2010-07-01	Common Stock	F	953	$18.45	Disposed	4388	Direct
2010-08-30	Common Stock	M	706	—	Acquired	4388	Direct
2010-08-30	Common Stock	F	226	$17.50	Disposed	4388	Direct

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-07-01	Restricted Stock Unit	$	M	3000	Disposed		Common Stock (3000)	Direct
2010-08-30	Restricted Stock Unit	$	M	706	Disposed		Common Stock (706)	Direct

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 fully vest three years from grant date.

F4: The RSUs fully vest 1 year from the grant date