EMERSON ELECTRIC CO — Director's Dealing 2006

May 1, 2006

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2006-04-27

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
2006-04-27	Common Stock	S	15000	$24.28	Disposed	7191711	Indirect
2006-04-28	Common Stock	S	5000	$23.4558	Disposed	7186711	Indirect

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	1065182	Direct

Footnotes

F1: The sales were effected in multiple transactions, at varying prices, on April 27, 2006, as follows and as described in
Footnote 2 below: 213 shares at $23.93; 87 at $23.95; 100 at $23.96; 100 at $23.98; 300 at $23.99; 200 at $24.02; 400 at
$24.04; 200 at $24.05; 200 at $24.12; 200 at $24.13; 300 at $24.14; 500 at $24.15; 500 at $24.16; 900 at $24.17; 100 at
$24.18; 900 at $24.19; 1,600 at $24.20; 400 at $24.21; 800 at $24.22; 200 at $24.23; 300 at $24.24; 100 at $24.25; 500 at
$24.27; 100 at $24.28; 300 at $24.29; 500 at $24.30; 300 at $24.31; 600 at $24.32; 200 at $24.33; 100 at $24.34; and 300 at
$24.35.

F2: This footnote sets forth additional detail with respect to the transactions described in Footnote 1, as follows: 200 shares
at $24.36; 300 at $24.37; 300 at $24.41; 100 at $24.43; 200 at $24.47; 300 at $24.50; 100 at $24.51; 100 at $24.52; 300 at
$24.53; 100 at $24.55; 100 at $24.67; 200 at $24.69; 200 at $24.70; 100 at $24.71; 100 at $24.73; 200 at $24.74; and 600 at
$24.75. The weighted average sales price for these transactions was $24.2800 per share.

F3: The reported securities are owned directly by Astec America Inc. The Reporting Person is the ultimate parent company of
Astec America Inc.

F4: The sales were effected in multiple transactions, at varying prices, on April 28, 2006, as follows: 200 shares at $22.49; 200
at $22.57; 100 at $22.64; 300 at $22.65; 200 at $22.95; 100 at $23.25; 200 at $23.43; 100 at $23.45; 200 at $23.49; 300 at
$23.51; 400 at $23.56; 200 at $23.58; 100 at $23.59; 100 at $23.61; 100 at $23.64; 200 at $23.70; 200 at $23.71; 400 at
$23.72; 500 at $23.73; 400 at $23.79; 100 at $23.84; 100 at $23.85; and 300 at $23.89. The weighted average sales price for
these transactions was $23.4558 per share.

F5: The reported securities are owned directly by Emerson Electric Co.