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Exhibit 31.1

CERTIFICATIONS

I, Walter S. Nimmo, certify that:

1. I have reviewed this annual report on
Form 10-K of Inveresk Research Group, Inc (the
Company);

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 to make the statements made,
in light of the circumstances under which the 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 periods 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-15(e) and 15d-15(e)) for the Company and 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 is
    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 (as
    defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) that
    occurred during the Companys fourth 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 of internal control over financial reporting, 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.                                                                                                   



| |                         
| | ------------------------
| | /s/ WALTER S. NIMMO     
| |                         
| | Chief Executive Officer,
| | President and Director  

Date: February 20, 2004