Exhibit 15.1

LETTER REGARDING UNAUDITED INTERIM FINANCIAL INFORMATION

Board of Directors and Shareholders

STERIS Corporation

We are aware of the incorporation by
reference in the following Registration Statements and related Prospectuses of our report dated August 7, 2008 relating to the unaudited consolidated interim financial statements of STERIS Corporation and subsidiaries that are included in its
Form 10-Q for the quarter ended June 30, 2008:



|                   |  |                                                                                                                      
|------------------ |  | ---------------------------------------------------------------------------------------------------------------------
|RegistrationNumber |  | Description                                                                                                          
|333-40058          |  | Form S-8 Registration Statement  Nonqualified Stock Option Agreement between STERIS Corporation and Les C. Vinney   
|                   | 
|333-65155          |  | Form S-8 Registration Statement  STERIS Corporation 1998 Long-Term Incentive Compensation Plan                      
|                   | 
|333-32005          |  | Form S-8 Registration Statement  STERIS Corporation 1997 Stock Option Plan                                          
|                   | 
|333-06529          |  | Form S-3 Registration Statement  STERIS Corporation                                                                 
|                   | 
|333-01610          |  | Post-effective Amendment to Form S-4 on Form S-8  STERIS Corporation                                                
|                   | 
|33-91444           |  | Form S-8 Registration Statement  STERIS Corporation 1994 Equity Compensation Plan                                   
|                   | 
|33-91442           |  | Form S-8 Registration Statement  STERIS Corporation 1994 Nonemployee Directors Equity Compensation Plan             
|                   | 
|33-55976           |  | Form S-8 Registration Statement  STERIS Corporation 401(k) Plan                                                     
|                   | 
|333-63774          |  | Form S-8 Registration Statement  Nonqualified Stock Option Agreement between STERIS Corporation and Peter A. Burke  
|                   | 
|333-09733          |  | Form S-8 Registration Statement  STERIS Corporation 401(k) Plan                                                     
|                   | 
|333-101308         |  | Form S-8 Registration Statement  STERIS Corporation 2002 Stock Option Plan                                          
|                   | 
|333-91302          |  | Form S-8 Registration Statement  Nonqualified Stock Option Agreement between STERIS Corporation and Mark D. McGinley
|                   | 
|333-137167         |  | Form S-8 Registration Statement  STERIS Corporation Deferred Compensation Plan                                      
|                   | 
|333-136239         |  | Form S-8 Registration Statement  STERIS Corporation 2006 Long-Term Equity Incentive Plan                            

/s/    ERNST & YOUNG
LLP

Cleveland, Ohio

August 7, 2008