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 November 6, 2007 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 September 30, 2007:



|                   |  |                                                                                                                                                                                                                  
|------------------ |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|RegistrationNumber |  | Description                                                                                                                                                                                                      
|                   | 
|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                                                                                                                        
|                   | 
|333-40058          |  | Form S-8 Registration Statement  Nonqualified Stock Option Agreement between STERIS Corporation and Les C. Vinney                                                                                               
|                   | 
|333-40082          |  | Form S-8 Registration Statement  Nonqualified Stock Option Agreement between STERIS Corporation and Laurie Brlas and the Nonqualified Stock Option Agreement between STERIS Corporation and
David L. Crandall   
|                   | 
|333-65155          |  | Form S-8 Registration Statement  STERIS Corporation 1998 Long-Term Incentive Compensation Plan                                                                                                                  
|                   | 
|333-55839          |  | Form S-8 Registration Statement  Nonqualified Stock Option Agreement between STERIS Corporation and John Masefield and the Nonqualified Stock Option Agreement between STERIS Corporation
and Thomas J. DeAngelo
|                   | 
|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 Registration Statement  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                                                                                                                                                 
|                   | 
|33-55258           |  | Form S-8 Registration Statement  STERIS Corporation Amended and Restated Non-Qualified Stock Option Plan                                                                                                        
|                   | 
|333-63770          |  | Form S-8 Registration Statement  Nonqualified Stock Option Agreement between STERIS Corporation and Charles L. Immel and Restricted Shares Agreement between STERIS Corporation and Charles
L. Immel            
|                   | 
|333-09733          |  | 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                                                                                              
|                   | 
|333-101308         |  | 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                                                                                            

/s/    ERNST & YOUNG
LLP

Cleveland, Ohio

November 6, 2007