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Electronic                                        1077 Business Center Circle
Sensor                                            Newbury Park, California 91320
Technology                                        Tel. (805) 480-1994
                                                  FAX (805) 480-1984

October 3, 2005



James Frey
1305 Ballantre Court
McClean, VA 22101


Dear Jim:


          On February 21, 2005, you entered into a letter agreement with
Electronic Sensor Technology, Inc., a Nevada Corporation (the "Company"),
pursuant to which the Company appointed you to the position of Chairman of the
Board of Directors for the Company for a two year term (the "Letter Agreement").
To induce you to serve as Chairman of the Board of Directors of the Company, the
Company made certain assurances to you regarding equity compensation
("Assurances") and purported to execute on those assurances by means of the
Letter Agreement. Following the execution and delivery of the Letter Agreement,
each of you and the Company have concluded that the Letter Agreement did not
satisfy the Assurances. Accordingly, as no meeting of the minds has occurred,
each of you and Company agree that the Letter Agreement is null and void and
that each of you and the Company shall be restored to your and its respective
position prior to the execution and delivery of the Letter Agreement.

          Until such time, if any, as (i) you and the Company shall enter into a
new agreement, (ii) you resign or are replaced as Chairman of the Board of
Directors or (iii) you cease being a director of the Company, you shall continue
to serve as Chairman of the Board of Directors of the Company. Execution by you
of this letter (which may be in counterparts) in the space provided below shall
indicate your agreement to the terms outlined above. This letter is to be
construed and enforced in accordance with the internal laws of the State of
Nevada and contains the entire agreement of the parties with respect to the
subject mater hereof. This letter may not be assigned by either party.


AGREED TO AND ACCEPTED:                           ELECTRONIC SENSOR TECHNOLOGY,
                                                  INC.


/s/ James Frey                                    By:     /s/ Matthew S. Collier
------------------------------------------           ---------------------------
James Frey                                        Matthew S. Collier
                                                  President and Chief Executive
                                                  Officer