TERM NOTE A

$2,000,000                                                     January ___, 1996


         FOR VALUE RECEIVED, undersigned,  EDITEK, INC., a Delaware corporation,
PSYCHIATRIC  DIAGNOSTIC  LABORATORIES OF AMERICA,  INC., a Delaware corporation,
and DIAGNOSTIX, a Delaware corporation (collectively,  the "Borrowers"),  hereby
unconditionally  jointly  and  severally  promise  to pay to the order of HELLER
FINANCIAL,  INC., a Delaware corporation (the "Lender"),  at the Lender's office
located at 500 West Monroe Street,  Chicago,  Illinois  60661,  or at such other
place as the holder of this Note may from time to time designate in writing,  in
lawful money of the United States of America and in immediately available funds,
the principal sum of TWO MILLION DOLLARS  ($2,000,000),  payable in installments
on the dates and in the  amounts  set forth in that  certain  Loan and  Security
Agreement of even date herewith, between the Borrowers and the Lender (the "Loan
Agreement"; capitalized terms used herein and not otherwise specifically defined
herein shall have the meanings assigned to them in the Loan Agreement).

         This Note is a Term Note referred to in  subsection  2.1(E) of the Loan
Agreement and is issued to evidence the Term Loan A made to the Borrowers by the
Lender pursuant to the provisions of the Loan  Agreement,  to which reference is
hereby made for a statement of the terms,  conditions and covenants  under which
the loan  evidenced  hereby  was made and is to be  repaid,  including,  but not
limited to, those  related to the mandatory  prepayment of the principal  hereof
and the acceleration of the indebtedness  represented hereby upon the occurrence
of an Event of Default or upon the  termination  of the  financing of which this
Note is part  pursuant to the Loan  Agreement.  Payment of this Note is secured,
inter alia, by the Collateral.

         The  Borrowers  jointly and  severally  promise to pay  interest on the
outstanding  unpaid  principal  amount  hereof  at the rate and on the dates set
forth in the Loan  Agreement.  Interest shall be computed on the daily principal
balance on the basis of a 360-day year for the actual  number of days elapsed in
the period during which it accrues.

         In no contingency or event whatsoever shall interest charged hereunder,
however such interest may be characterized or computed,  exceed the highest rate
permissible  under any law which a court of competent  jurisdiction  shall, in a
final  determination,  deem  applicable  hereto.  In the event that such a court
determines  that the Lender has  received  interest  hereunder  in excess of the
highest rate applicable  hereto,  the provisions of the Loan Agreement  relating
thereto shall control.

         The Borrowers  hereby waive  demand,  presentment,  protest,  notice of
demand,  dishonor,  presentment,  protest,  nonpayment  and all other notices in
connection with this Note.



         If this Note is collected by or through an  attorney-at-law,  all costs
of collection,  including  reasonable  attorneys'  fees, shall be payable by the
undersigned.



         THIS NOTE HAS BEEN  DELIVERED  AT AND SHALL BE DEEMED TO HAVE BEEN MADE
AT CHICAGO, ILLINOIS, AND SHALL BE INTERPRETED AND THE RIGHTS AND LIABILITIES OF
THE PARTIES HERETO  DETERMINED IN ACCORDANCE  WITH THE INTERNAL LAWS (AS OPPOSED
TO CONFLICTS OF LAW PROVISIONS) AND DECISIONS OF THE STATE OF ILLINOIS. Whenever
possible each  provision of this Note shall be  interpreted in such manner as to
be effective and valid under  applicable  law, but if any provision of this Note
shall be prohibited by or invalid under  applicable law, such provision shall be
ineffective  to  the  extent  of  such   prohibition   or  invalidity,   without
invalidating the remainder of such provision or the remaining provisions of this
Note.  Whenever in this Note  reference is made to the Lender or the  Borrowers,
such reference shall be deemed to include,  as applicable,  a reference to their
respective  successors and assigns. The provisions of this Note shall be binding
upon  and  shall  inure to the  benefit  of such  successors  and  assigns.  The
Borrowers' successors and assigns shall include, without limitation, a receiver,
trustee or debtor in possession of or for the Borrowers.

                      [Signatures appear on following page]





         WITNESS  the  hand and seal of the  undersigned,  as of the date  first
above written.

                                               EDITEK, INC.

                                               By:

                                               Title:

                                               Attest:

                                               Title:

                                                     [CORPORATE SEAL]

                                               PSYCHIATRIC DIAGNOSTIC 
                                               LABORATORIES OF AMERICA, INC.

                                               By:

                                               Title:

                                               Attest:

                                               Title:

                                                     [CORPORATE SEAL]

                                               DIAGNOSTIX, INC.

                                               By:

                                               Title:

                                               Attest:

                                               Title:

                                                     [CORPORATE SEAL]