EMERSON ELECTRIC CO — Director's Dealing 2006

May 5, 2006

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2006-05-03

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
2006-05-03	Common Stock	S	40119	$23.8872	Disposed	7044434	Indirect
2006-05-04	Common Stock	S	44379	$24.5750	Disposed	7000055	Indirect

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	1065182	Direct

Footnotes

F1: The sales were effected in multiple transactions, at varying prices, on May 3, 2006, as follows and as described in Footnote
2 below: 600 shares at $23.48; 100 at $23.49; 100 at $23.50; 500 at $23.62; 100 at $23.63; 100 at $23.64; 400 at $23.67; 200
at $23.68; 100 at $23.69; 200 at $23.70; 100 at $23.71; 100 at $23.73; 500 at $23.74; 200 at $23.75; 200 at $23.76; 700 at
$23.78; 518 at $23.79; 800 at $23.80; 1,000 at $23.81; 1,900 at $23.82; 900 at $23.83; 1,700 at $23.84; 1,360 at $23.85;
3,900 at $23.86; 2,600 at $23.87; 2,884 at $23.88; 1,300 at $23.89; and 1,800 at $23.90.

F2: This footnote sets forth additional detail with respect to the transactions described in Footnote 1, as follows: 2,364
shares at $23.91; 1,136 at $23.92; 200 at $23.93; 900 at $23.94; 993 at $23.95; 843 at $23.96; 400 at $23.97; 900 at $23.98;
921 at $23.99; 1,067 at $24.00; 1,633 at $24.01; 200 at $24.02; 300 at $24.03; 100 at $24.04; 500 at $24.05; 200 at $24.06;
100 at $24.07; 300 at $24.08; 200 at $24.09; 500 at $24.10; 800 at $24.11; 300 at $24.12; 200 at $24.13; and 200 at $24.16.
The weighted average sales price for these transactions was $23.8872 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 May 4, 2006, as follows and as described in Footnote
5 below: 100 shares at $24.20; 500 at $24.23; 200 at $24.24; 899 at $24.25; 13 at $24.26; 201 at $24.27; 200 at $24.28; 200
at $24.29; 100 at $24.30; 387 at $24.32; 400 at $24.33; 100 at $24.36; 199 at $24.38; 200 at $24.39; 300 at $24.40; 800 at
$24.41; 100 at $24.42; 700 at $24.44; 190 at $24.45; 290 at $24.46; 792 at $24.47; 1,000 at $24.48; 1,700 at $24.49; 1,108
at $24.50; 800 at $24.51; 1,100 at $24.52; 2,000 at $24.53; 699 at $24.54; and 1,100 at $24.55.

F5: This footnote sets forth additional detail with respect to the transactions described in Footnote 4, as follows: 600 shares
at $24.56; 1,701 at $24.57; 2,700 at $24.58; 2,100 at $24.59; 700 at $24.60; 500 at $24.61; 800 at $24.62; 1,500 at $24.63;
300 at $24.64; 1,500 at $24.65; 2,300 at $24.66; 1,200 at $24.67; 2,500 at $24.68; 6,500 at $24.69; 1,000 at $24.70; 200 at
$24.71; 1,400 at $24.73; and 500 at $24.74. The weighted average sales price for these transactions was $24.5750 per share.

F6: The reported securities are owned directly by Emerson Electric Co.