Ownership Submission
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 OF SECURITIES

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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(Print or Type Responses)
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 (Month/Day/Year)
05/21/2013
(Street)

MENTOR, OH 44060		 4. If Amendment, Date Original Filed(Month/Day/Year)
 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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 05/21/2013   M   4,650 A $ 30.84 12,677 D  
Common Shares, No Par Value 05/21/2013   S   4,650 D $ 45.9307 (1) 8,027 D  
Common Shares, No Par Value 05/21/2013   M   1,500 A $ 22.83 9,527 D  
Common Shares, No Par Value 05/21/2013   S   1,500 D $ 46.0473 (6) 8,027 (2) D  
Common Shares, No Par Value               500 I See Footnote Below. (3)
Common Shares, No Par Value               634 I See Footnote Below. (4)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 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
(Month/Day/Year)		 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 $ 30.84 05/21/2013   M     4,650   (5) 05/21/2018 Common Shares, No Par Value 4,650 $ 0 0 D  
Employee Stock Option Exercise $ 22.83 05/21/2013   M     1,500 05/21/2013 05/21/2019 Common Shares, No Par Value 1,500 $ 0 0 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
AAMOTH WILLIAM L
5960 HEISLEY ROAD
MENTOR, OH 44060		       V P - Corporate Treasurer  

Signatures

 /s/ Dennis P. Patton, Authorized Representative under Power of Attorney   05/22/2013
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) This represents the average sales price of the shares sold. The actual 27 sales prices ranged from $45.6700 per share to $46.1500 per share. Issuer, upon request by the SEC staff, will provide full information regarding the number of shares sold at each of these 27 sales prices.
(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 647.872 units of the STERIS Corporation 401(k) Plan STERIS Stock Fund which equals 634 Common share equivalents as of May 21, 2013.
(5) These options became exercisable as follows: 1,162 on May 21, 2009, 1,162 on May 21, 2010, 1,163 on May 21, 2011 and 1,163 on May 21, 2012.
(6) This represents the average sales price of the shares sold. The actual 7 sales prices ranged from $45.9800 per share to $46.1500 per share. Issuer, upon request by the SEC staff, will provide full information regarding the number of shares sold at each of these 7 sales prices.

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