Exhibit 31

                   Certifications Under Rule 13a-14(a)/l5d-14(a)


  I, Henry C. Pao, certify that:

  1.  I have reviewed this annual report on Form 10-K of Supertex, Inc., a
  California corporation;

  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 such
  statements were made, not misleading with respect to the period covered by
  this annual report;

  3.  Based on my knowledge, the financial statements, and other financial
  information included in this annual 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 annual report;

  4.  I am 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 I have:

    (a) designed such disclosure controls and procedures, or caused such
    disclosure controls and procedures to be designed under my 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 annual report is
    being prepared;

    (b) evaluated the effectiveness of the registrant's disclosure controls and
    procedures and presented in this report my conclusion 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 registrant's internal
    control over financial reporting that occurred during the registrant's
    fourth fiscal quarter that has materially affected, or is reasonably likely
    to materially affect, the registrant's internal control over financial
    reporting; and

  5.  I have disclosed, based on my most recent evaluation of internal control
  over financial reporting, to the registrant's auditors and the audit
  committee of registrant's board of directors (or persons performing the
  equivalent function):

    (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 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 control
    over financial reporting.


June 16, 2004                      /s/ Henry C. Pao
                                   -------------------------
                                   Henry C. Pao, Ph.D
                                   Chief Executive Officer and Chief
                                   Financial Officer
                                  (Principal Executive and Financial Officer)