EXHIBIT 31 (a)

CERTIFICATIONS

In connection
with the Annual Report on Form 10-K of Enzo Biochem, Inc. (the Company) for
the fiscal year ended July 31, 2009 as filed with the Securities and Exchange
Commission on the date hereof, I, Elazar Rabbani, Ph.D., Chief Executive
Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted
pursuant to § 302 of the Sarbanes-Oxley Act of 2002, that:

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|1. | I have
 reviewed this Annual Report on Form 10-K of Enzo Biochem, Inc.                                                                                                                                                                                                                                                                 
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|2. | Based on my
 knowledge, this 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 report;                         
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|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;                                               
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|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)) and internal control over financial
 reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the
 Company and have:
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|   | (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;
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|   | (b)                                                                                                                                                                                                                                                                                                                                     | Designed
 such internal control over financial reporting, or caused such internal
 control over financial reporting to be designed under our supervision, to
 provide reasonable assurance regarding the reliability of financial reporting
 and the preparation of financial statements for external purposes in
 accordance with generally accepted accounting principles;    
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|   | (c)                                                                                                                                                                                                                                                                                                                                     | 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                                                                                            
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|   | (d)                                                                                                                                                                                                                                                                                                                                     | 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 (the
 Companys fourth fiscal quarter in the case of an annual report) that has
 materially affected, or is reasonably likely to materially affect, the
 Companys internal control over financial reporting; and
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|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
 (or persons performing the equivalent functions):                                             
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|   | (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.                                                                                                                                                                                                      

|                        |                          |                           
|----------------------- | ------------------------ | --------------------------
|Date:
 October 14, 2009 |                          |                           
|                        | By:                      | /s/ Elazar
 Rabbani, Ph.D.
|                        |                          |                           
|                        | Elazar
 Rabbani, Ph.D.  
|                        | Chief
 Executive Officer

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