MKS INC — Director's Dealing 2011

Feb 17, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2011-02-16

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

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-02-16	Common Stock	M	823	$20.02	Acquired	848	Direct
2011-02-16	Common Stock	S	823	$30.22	Disposed	25	Direct
2011-02-16	Common Stock	M	436	$18.44	Acquired	461	Direct
2011-02-16	Common Stock	S	436	$30.22	Disposed	25	Direct
2011-02-16	Common Stock	M	375	$18.12	Acquired	400	Direct
2011-02-16	Common Stock	S	375	$30.29	Disposed	25	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-02-16	Stock Option (Right to Buy)	$20.02	M	823	Disposed	2011-10-15	Common Stock (823)	Direct
2011-02-16	Stock Option (Right to Buy)	$18.44	M	436	Disposed	2012-06-24	Common Stock (436)	Direct
2011-02-16	Stock Option (Right to Buy)	$18.12	M	375	Disposed	2013-05-29	Common Stock (375)	Direct

Footnotes

F1: This transaction was executed in multiple trades at prices ranging from $30.28 to $30.29. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide, upon request, the full information regarding the number of shares and prices at which the transaction was effected.

F2: Vests as follows: 33 1/3 after the first year and each successive 12 month period thereafter.

F3: Vests 100% one year after grant

F4: 25% after first year, 6.25% each quarter thereafter - total 4 years.