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: Eyerman Paul (VP & GM, ENI and Medical)

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-08-30	Common Stock	M	2647	—	Acquired	2234	Direct
2010-08-30	Common Stock	F	961	$17.50	Disposed	2234	Direct
2010-11-30	Common Stock	A	448	$16.19	Acquired	2234	Direct

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-08-30	Restricted Stock Unit	$	M	2647	Disposed		Common Stock (2647)	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: These shares were acquired under the MKS employee stock purchase plan.

F4: The RSUs vest in one year from the August 28, 2009 grant date.