Exhibit 31.1



CERTIFICATION OF CHIEF EXECUTIVE OFFICER



I, Ming Hsieh, President and Chief Executive Officer of Cogent, Inc. (the Registrant), certify that:



1. I have reviewed this quarterly report on Form 10-Q of the Registrant;



2. Based on my knowledge, this quarterly 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 such statements were made, not misleading with respect to the period covered by this
quarterly report;



3. Based on my knowledge, the financial
statements, and other financial information included in this quarterly report, fairly present in all material respects the financial condition, results of operations and cash flows of the Registrant as of, and for, the periods presented in this
quarterly report;



4. The Registrant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 Registrant 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 Registrant, including its consolidated subsidiaries, is made known to us by others within those entities,
particularly during the period in which this quarterly report is being prepared;



(b) evaluated the effectiveness of the Registrant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 quarterly report any change in the Registrants internal control over financial reporting that occurred during
the Registrants most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, the Registrants internal control over financial reporting; and



5. The Registrants other certifying officer and I have disclosed, based
on our most recent evaluation of internal control over financial reporting, to the Registrants auditors and the audit committee of Registrants board of directors:



(a) all significant deficiencies and material weaknesses in the design or operation of internal controls
over financial reporting which are reasonably likely to adversely affect the Registrant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 Registrants internal controls over financial reporting.



Dated: August 11, 2005



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|/s/    Ming Hsieh                                                             
|Ming Hsieh President and Chief Executive Officer (Principal Executive Officer)