EMERSON ELECTRIC CO — Director's Dealing 2006

Mar 31, 2006

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2006-03-29

Reporting Person: EMERSON ELECTRIC CO (10% Owner)
Reporting Person: ASTEC AMERICA INC (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2006-03-29	Common Stock	S	15000	$23.2516	Disposed	7491711	Indirect
2006-03-30	Common Stock	S	15000	$23.1556	Disposed	7476711	Indirect

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	1065182	Direct

Footnotes

F1: The sales were effected in multiple transactions, at varying prices, on March 29, 2006, as follows: 2,248 shares at $23.23;
1,000 at $23.24; 6,206 at $23.25; 3,200 at $23.26; and 2,346 at $23.27. The weighted average sales price for these
transactions was $23.2516 per share.

F2: The reported securities are owned directly by Astec America Inc. The Reporting Person is the ultimate parent company of
Astec America Inc.

F3: The sales were effected in multiple transactions, at varying prices, on March 30, 2006, as follows: 100 shares at $23.07; 100
at $23.08; 300 at $23.09; 1,300 at $23.10; 700 at $23.11; 1,700 at $23.12; 1,100 at $23.13; 700 at $23.14; 2,600 at $23.15;
1,500 at $23.16; 900 at $23.17; 900 at $23.18; 412 at $23.19; 688 at $23.20; 700 at $23.21; 100 at $23.22; 200 at $23.23;
400 at $23.24; 200 at $23.26; 100 at $23.27; 100 at $23.29; and 200 at $23.30. The weighted average sales price for these
transactions was $23.1556 per share.

F4: The reported securities are owned directly by Emerson Electric Co.