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, 2004 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. ss. 1350, as
adopted pursuant to ss. 302 of the Sarbanes-Oxley Act of 2002, that:

1.    I have reviewed this Annual Report on Form 10-K of Enzo Biochem, Inc.

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;

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(s)  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:

      (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)   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 principals;

      (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

      (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

5.    The Company's other certifying  officer(s) 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):

      (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, 2004

                                                   By: /s/ Elazar Rabbani, Ph.D.
                                                       -------------------------
                                                   Elazar Rabbani, Ph.D.
                                                   Chief Executive Officer