Applied Signal Technology, Inc.
  Exhibit 31.1

I, Gary Yancey, Chief Executive
  Officer of the registrant, certify that:

1. I have reviewed this quarterly
  report on Form 10-Q of Applied Signal Technology, 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 in order 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 registrant as of, and for, the periods presented
  in this report;

4. The registrants other
  certifying officers and I are responsible for establishing and maintaining disclosure
  controls and procedures (as defined in Exchange Act Rules 13a-15e and 15d-15e)
  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 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;

(c) Disclosed in this report
  any change in the registrants internal control over financial reporting
  that occurred during the registrants most recent fiscal quarter (the registrants
  fourth quarter in the case of an annual report) 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 officers 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 the 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 controls over financial reporting.



|/s/ Gary L. Yancey
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          Gary L. Yancey, Chief Executive Officer |  | September
      12, 2003
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