EXHIBIT 15.1 LETTER RE: 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 12, 2002,
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, 2002:

|Registration Number | Description                                                                                                                                                                                                      
|------------------- | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|333-91302           | Form S-8 Registration Statement - Nonqualified Stock Option Agreement between STERIS Corporation and Mark. D. McGinley                                                                                           
|333-63774           | Form S-8 Registration Statement - Nonqualified Stock Option Agreement between STERIS Corporation and Peter A. Burke                                                                                              
|333-63772           | Form S-8 Registration Statement - Nonqualified Stock Option Agreement between STERIS Corporation and Thomas J. Magulski                                                                                          
|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            
|333-40082           | 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   
|333-40058           | 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                                                                                                                  
|333-55839           | 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 - 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 - STERIS Corporation Amended and Restated Non-Qualified Stock Option                                                                                                                       

/s/ Ernst & Young
LLP

Cleveland, Ohio November 12, 2002