(10)  (b)       Employment Agreement dated July 14, 1997 by and
                              between John C. Landon and Diagnon Corporation.



<PAGE>


                                   EMPLOYMENT AGREEMENT

THIS AGREEMENT made as of this 14th day of July, 1997, by and between DIAGNON
CORPORATION, a Delaware Corporation, hereinafter referred to as "Diagnon" and
Dr. John Landon, hereinafter referred to as "Dr. Landon".

      WHEREAS Dr. Landon is currently serving as President, Chief Executive
Officer, a member of the Executive Committee and as a director of Diagnon and

      WHEREAS the Board of Directors of Diagnon recognized that Dr. Landon's
contribution to the growth and success of Diagnon, has been substantial and

      WHEREAS Diagnon wishes to assure continued employment of Dr. Landon in
these positions pursuant to the terms and conditions hereinafter set forth,
and

      WHEREAS, these terms and conditions are satisfactory to Dr. Landon.
NOW, THEREFORE, the parties hereto agree as follows:

1. Employment. Diagnon hereby employs Dr. Landon as its President, Chief
Executive Officer, a member of its Executive Committee and as director of
Diagnon upon the terms and conditions herein after set forth. Dr. Landon will
also serve as President and Chief Executive of its subsidiaries Enhanced
Therapeutics, Inc. and BIOQUAL, Inc. As President and Chief Executive Officer,
Dr. Landon shall be subject to the direction and control of the Board of
Directors of Diagnon.

2. Compensation. For this services rendered under this Agreement Dr. Landon
shall receive a base salary of $275,000 per year. The following incentive
compensation is a part of their agreement:

      (a) A bonus determined by the Board of Directors based on a variety of
      criteria that are unspecified, may be made available after close of each
      Fiscal Year. This will be capped at $40,000, unless changed by the
      Compensation Committee.

      (b) A Split Dollar Whole Life Insurance policy for $1,000,000 will be
      carried for Dr. Landon with beneficiary designated by Dr. Landon.

      (c) An individual disability insurance policy will be carried for Dr.
      Landon, supplementing the group insurance disability.

      (d) Additional incentive compensation may be provided at the discretion of
      the Board of Directors and/or the Compensation Committee.

3. Conditions of Employment and Fringe Benefits. Dr. Landon shall be entitled to
vacations, sick leave, and fringe benefits consistent with the policies of
Diagnon, in addition to those fringe benefits to which Dr. Landon is entitled as
President and Chief Executive Officer of BIOQUAL, Inc. and Enhanced
Therapeutics, Inc., if any.

4. Terms of Employment. Unless terminated earlier pursuant to the provisions of
the Agreement, the Agreement shall remain in effect for a five (5) year period.
If there is a "change of control of Diagnon", the Agreement shall remain in
effect for the remainder of the five (5) year period or an


<PAGE>


                                            2

additional 2 1/2 years, whichever is greater. For the purpose of this Agreement
a "change in control" shall be considered to occur whenever, as a result of a
change in ownership of Diagnon stock, individuals who are currently members of
the Board of Directors cease for any reason to constitute at least a majority of
the Board of Directors of Diagnon unless the election of individuals who are not
currently directors has been approved in advance by at least two thirds of the
current directors of Diagnon. This Agreement may be terminated prior to the end
of its five year term under the following circumstances:
      (a) upon the death of Dr. Landon during the term of this agreement;
      (b) in the event that Dr. Landon incurs a disability which is an injury or
a sickness which restricts his ability to perform the material and substantial
duties as President and Chief Executive Officer and prevents him from working on
a full-time basis on behalf of Diagnon for a period in excess of six consecutive
months;
      (c)  in the event that Diagnon and Dr. Landon mutually agree to the
termination of employment;
      (d) in the event that Dr. Landon is discharged for cause. Dr. Landon will
be considered to have been discharged for cause in the event (i) he is convicted
of any offense punishable as a felony, (ii) he admits in writing to the
commission of a crime against Diagnon or (iii) he engages in activities which
compete with the business of Diagnon.
      (e) Dr. Landon may terminate his employment hereunder in the event of a
failure by Diagnon to comply with any material provision of the Agreement which
has not been cured within ten (10) days after notice of such noncompliance has
been given by Dr. Landon to Diagnon's Board of Directors.

5. Notice of Termination. Any termination of Dr. Landon's employment by Diagnon
or by Dr. Landon (other than termination due to the death of Dr. Landon) shall
be communicated by written Notice of Termination to the other party hereto. For
purposes o this Agreement, a "Notice of Termination" shall mean a notice which
shall indicate the specific termination provision in the agreement relied upon
and shall set forth in reasonable detail the facts and circumstances claimed to
provide a basis for termination of Dr. Landon's employment under the provision
as indicated.

The date of termination shall be determined as follows;

      (a) if Dr. Landon's employment is terminated by his death, the date of
this death;
      (b) if Dr. Landon's employment is terminated due to disability, the sixth
month anniversary of the date Dr. Landon was first absent from work due to the
disability, provided, that he has not returned to the performance of his duties
on a full-time basis during such time; and
      (c) if Dr. landon's employment is terminated for any other reason, the
date specified in the Notice of Termination.

      If within thirty (30) days after any Notice of Termination is given, the
party receiving such Notice of Termination notifies the other party that a
dispute exist concerning the termination, the date of the termination shall have
been deemed the date on which the dispute is finally resolved, either by mutual
written agreement of the parties, by a binding and final arbitration award, or
by final judgement, order or decree of a court of competent jurisdiction (the
time for appeal therefrom having expired and no appeal having been taken).


<PAGE>


                                            3


6. Compensation Upon Termination

      (a) If Dr. Landon's employment is terminated by his death, Diagnon shall
pay to his estate the total compensation which otherwise would have been payable
to Dr. Landon for the twelve month period following the date of his death.
Payments to his estate shall be made bi-weekly.

      (b) If Dr. Landon is unable to perform his duties hereunder as a result of
incapacity due to disability, he shall continue to receive his salary until his
employment is terminated pursuant to Paragraph 5(b) above.

      (c) If Dr. Landon is terminated for cause, or if Diagnon and Dr. Landon
mutually agree to terminate Dr. Landon's employment, the date stated in the
Notice of Termination shall be the date employment is terminated and thereafter
Diagnon shall have no further obligation to Dr. Landon under this Agreement.

7. Agreement Not To Compete. Dr. Landon agrees that during the term of this
employment by Diagnon and or a period of three (3) years following termination
of employment, so long as Diagnon has not breached this Agreement, he will not,
directly or indirectly, engage in activities competitive with the activities of
Diagnon, either as sole proprietor, partner, stockholder, officer, director,
agent, consultant, independent contractor, or in any other capacity with the
exception of government contract work in the scientific field in which Dr.
Landon has been normally making a livelihood. In the event of breach of this
Agreement Diagnon shall have the right to injunctive relief against such
violation, as well as any other rights and remedies provided by law. In this
connection Dr. Landon acknowledges that his services are unique and that
monetary damages may not adequately compensate Diagnon for its losses resulting
from violation of this agreement not to compete.

8. Confidential Information. Dr. landon shall keep confidential any trade
secrets or other confidential information derived as a result of his services on
behalf of Diagnon and, on termination of his employment, will turn over to
Diagnon all document's relating to his employment by Diagnon and the business
activities of Diagnon except those documents in which Dr. Landon has a
proprietary interest (e.g., copies of professional papers, transcripts of
speeches, etc.).

9. Notices. Any notices required to be given pursuant to this Agreement shall be
in writing and shall be sent by registered or certified mail, return receipt
requested, to the parties at the following addresses:

If to Diagnon delivered or addressed to:

      Diagnon Corporation
      9600 Medical Center Drive
      Rockville, Maryland  20850

With a copy delivered or addressed to:
      Mr. Kevin O'Neill
      9600 Medical Center Drive
      Rockville, Maryland  20850



<PAGE>


                                            4
If to Dr. Landon, addressed to:
      Dr. John C. Landon
      8213 Raymond Lane
      Potomac, Maryland  20854

With a copy to:
      Mr. Andrew Mishkin
      1350 I Street, N.W., Suite 700
      Washington, D.C.  20005

10. Arbitration. Any controversy or claim arising out of or relating to this
contract, or breach thereof, shall be settled by arbitration in accordance with
the Commercial Arbitration Rules of the American Arbitration Association, and
judgement upon the award rendered by the Arbitration(s) may be entered in any
Court having jurisdiction thereof.

11. Renewal. At the option of Diagnon, the employment of Dr. Landon may be
renewed from year to year under such terms and conditions as are mutually agreed
to by Diagnon and Dr. Landon. Diagnon shall require any successor to all or
substantially all of the business and/or assets of Diagnon expressly to assume
and agree to perform this Agreement in the same manner and to the same extent
that Diagnon would be required to perform if not such succession had been taken.

This agreement shall be binding upon the parties hereto and their respective
heirs, successors and permitted assigns.


IN WITNESS WHEREOF the undersigned have executed this Agreement as of this day
14th of July, 1998.


ATTEST                                    DIAGNON CORPORATION


/s/ Michael P. O'Flaherty           BY:  /s/ Charles F. Gauvin
____________________________            ____________________________

/s/ Michael P. O'Flaherty           BY:  /s/ Charles C. Francisco
____________________________            ____________________________

/s/ Michael P. O'Flaherty           BY:  /s/ J. Thomas August
____________________________            ____________________________

                                    BY:
____________________________            ____________________________


WITNESS

/s/ Michael P. O'Flaherty                /s/ John C. Landon
____________________________            ____________________________
                                           Dr. John C. Landon