Sec Form 4 Filing - AAMOTH WILLIAM L @ STERIS CORP - 2012-09-21

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person AAMOTH WILLIAM L 2. Issuer Name and Ticker or Trading Symbol STERIS CORP [ STE] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) V P - Corporate Treasurer (Last) (First) (Middle) 5960 HEISLEY ROAD 3. Date of Earliest Transaction (MM/DD/YY) 09/21/2012 (Street) MENTOR, OH44060 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Shares, No Par Value 09/21/2012 M 4,157 A $ 24.72 12,184 D Common Shares, No Par Value 09/21/2012 S( 1 ) 4,157 D $ 35.7211 8,027 ( 2 ) D Common Shares, No Par Value 500 I See Footnote Below. ( 3 ) Common Shares, No Par Value 635 I See Footnote Below. ( 4 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Employee Stock Option Exercise $ 24.72 09/21/2012 M 4,157 ( 5 ) 09/12/2016 Common Shares, No Par Value 4,157 $ 0 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other AAMOTH WILLIAM L 5960 HEISLEY ROAD MENTOR, OH44060 V P - Corporate Treasurer Signatures /s/ Dennis P. Patton, Authorized Representative under Power of Attorney 09/24/2012 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These open market sales of a total of 4,157 Common Shares is pursuant to a Rule 10b5-1 Stock Trading Plan entered into by the Reporting Person on August 3, 2012. ( 2 )5,280 of these Common Shares are restricted. The restrictions on these Common Shares lapse as follows: 2,680 on May 20, 2014, 500 on May 31, 2013, 500 on June 2, 2014, 500 on June 1, 2015, 275 on May 30, 2013, 275 on May 30, 2014, 275 on June 1, 2015 and 275 on May 31, 2016. ( 3 )Represents an investment by Mr. Aamoth in his Vanguard William L. Aamoth - Rollover IRA Brokerage Account. ( 4 )Represents 648.113 units of the STERIS Corporation 401(k) Plan STERIS Stock Fund which equals 635 Common share equivalents as of September 21, 2012. ( 5 )These options became exercisable as follows: 1,007 on September 12, 2007, 1,050 on September 12, 2008 1,050 on September 12, 2009 and 1,050 on September 12, 2010.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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