MKS INC — Director's Dealing 2011

Mar 31, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2011-03-30

Reporting Person: COLELLA GERARD G (VP, Chief Operating Officer)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-03-30	Common Stock	M	28000	$27.11	Acquired	39600.272	Direct
2011-03-30	Common Stock	S	28000	$33.00	Disposed	11600.272	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-03-30	Stock Option (Right to Buy)	$27.11	M	28000	Disposed	2013-11-13	Common Stock (28000)	Direct

Footnotes

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

F2: 25% after first year, 6.25% each quarter thereafter - total 4 years.