MKS INC — Director's Dealing 2012

Mar 1, 2012

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2012-02-28

Reporting Person: Lee John Tseng-Chung (Sr. VP, Controls & PFMC)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2012-02-28	Common Stock	M	1892.072	—	Acquired	2383.424	Direct
2012-02-28	Common Stock	M	1332	—	Acquired	3715.424	Direct
2012-02-28	Common Stock	M	3750	—	Acquired	7465.424	Direct
2012-02-28	Common Stock	F	2212	$30.63	Disposed	5253.424	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2012-02-28	Restricted Stock Unit	$	M	1892.072	Disposed		Common Stock (1892.072)	Direct
2012-02-28	Restricted Stock Unit	$	M	1332	Disposed		Common Stock (1332)	Direct
2012-02-28	Restricted Stock Unit	$	M	3750	Disposed		Common Stock (3750)	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: These RSUs are subject to the achievement of performance criteria determined in the first year of the grant and thereafter vests in equal annual installments over three years.

F4: The RSUs vest in equal annual installments over three years.

F5: These RSUs are subject to the achievement of performance criteria determined in the first year of the grant and thereafter vests in equal annual installments of four years.