Exhibit 31.1

CERTIFICATION

I, George G.
Usher, Chief Executive Officer of Polydex Pharmaceuticals Limited (the
Company) do hereby certify that:

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| | 1. | I have
  reviewed this annual report on Form 10-K of the Company for the fiscal year
  ended January 31, 2005;                                                                                                                                                                                                                    
| |    |                                                                                                                                                                                                                                                                                                                                   
| | 2. | Based on my
  knowledge, this annual report does not contain any untrue statement of a
  material fact or omit to state a material fact necessary in order to make the
  statements made, in light of the circumstances under which such statements
  were made, not misleading with respect to the period covered by this report;
| |    |                                                                                                                                                                                                                                                                                                                                   
| | 3. | Based on my
  knowledge, the financial statements, and other financial information included
  in this report, fairly present in all material respects the financial
  condition, results of operations and cash flows of the Company as of, and
  for, the period presented in this report;                                       
| |    |                                                                                                                                                                                                                                                                                                                                   
| | 4. | The
  Companys other certifying officer and I are responsible for establishing and
  maintaining disclosure controls and procedures (as defined in Exchange Act
  Rules 13a-14 and 15d-14) for the Company and we have:                                                                                                          
| |    |                                                                                                                                                                                                                                                                                                                                   
| |    | (a)                                                                                                                                                                                                                                                                                                                                | designed
  such disclosure controls and procedures, or caused such disclosure controls
  and procedures to be designed under our supervision, to ensure that material
  information relating to the Company, including its consolidated subsidiaries,
  is made known to us by others within those entities, particularly during the
  period in which this report was being prepared;
| |    |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                       
| |    | (b)                                                                                                                                                                                                                                                                                                                                | evaluated
  the effectiveness of the Companys disclosure controls and procedures and
  presented in this report our conclusions about the effectiveness of the
  disclosure controls and procedures, as of the end of the period covered by
  this report based on such evaluation; and                                                                                              
| |    |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                       
| |    | (c)                                                                                                                                                                                                                                                                                                                                | disclosed in
  this report any change in the Companys internal control over financial
  reporting that occurred during the Companys most recent fiscal quarter that
  has materially affected, or is reasonably likely to materially affect the
  Companys internal control over financial reporting; and                                                                          
| |    |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                       
| | 5. | The
  Companys other certifying officer and I have disclosed, based on our most
  recent evaluation, to the Companys auditors and the audit committee of the
  Companys board of directors:                                                                                                                                    
| |    |                                                                                                                                                                                                                                                                                                                                   
| |    | (a)                                                                                                                                                                                                                                                                                                                                | all
  significant deficiencies and material weaknesses in the design or operation
  of internal control over financial reporting which are reasonably likely to
  adversely affect the Companys ability to record, process, summarize and
  report financial information; and                                                                                                        
| |    |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                       
| |    | (b)                                                                                                                                                                                                                                                                                                                                | any fraud,
  whether or not material, that involves management or other employees who have
  a significant role in the Companys internal control over financial
  reporting.                                                                                                                                                                                                         

|                         |                                  
|------------------------ | ---------------------------------
|Dated: 
  April 29, 2005 | /s/ George
  G. Usher            
|                         |                                  
|                         | Chief
  Executive Officer        
|                         | Polydex
  Pharmaceuticals Limited

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