Exhibit 10.42


                                    AGREEMENT

     THIS AGREEMENT, made this __3RD__ day of __SEPTEMBER,  '97__ by and between
DIANON  SYSTEMS,  INC.,  its  affiliates,  subsidiaries,  successors and assigns
(collectively  called  hereinafter  "DIANON") and Vernon L. Wells, an individual
residing at 10973 Chase Lane #B, St. Louis,  Missouri 63146 (hereinafter  called
"Employee").

     In consideration  of the commencement of Employee's  employment with DIANON
as Vice President of Sales,  the payment of  compensation  and benefits for such
employment,   and  access  to   sensitive   information,   Employee  and  DIANON
acknowledge,  represent and agree to the terms and  conditions set forth in this
Agreement.

     (1) Employee  agrees that, to the fullest extent  permitted by law, for the
period of one (1) year after the date of termination  of employment  with DIANON
(for whatever reasons),  Employee (a) will not solicit business on behalf of any
entity which is conducting any business  which  competes with DIANON's  business
("Competing  Entity"),  (b) will not solicit  business from customers of DIANON,
(c) will not solicit the  employment  or  services  or any of the  employees  of
DIANON,  (d) will not,  directly or  indirectly,  participate  in the ownership,
management,  operation or control of any Competing Entity in the geographic area
located  within  one  hundred  (100)  miles of DIANON  offices,  or in any other
geographic area in which Employee may have rendered service to DIANON during the
two (2) year period prior to the termination of employment.

     (2) Employee's  employment  with DIANON creates a relationship of trust and
confidence  between the parties.  Employee agrees that, during and after his/her
employment with DIANON,  Employee will not use or disclose, or allow anyone else
to use or disclose, any confidential information relating to the products, sales
and/or business  affairs of DIANON or of any customer or supplier of DIANON,  or
any information created,  discovered, or developed by or for DIANON, or acquired
by DIANON,  that has  commercial  value in DIANON's  present or future  business
("Confidential  Information"),  except as may be necessary in the performance of
Employee's  employment  with  DIANON  or as  may be  authorized  in  advance  by
appropriate  officials of DIANON.  By way of  illustration,  but not limitation,
Confidential   Information   includes  processes,   formulas,   data,  know-how,
inventions,   improvements,   techniques,   marketing   plans,   product  plans,
strategies,  forecasts,  customer lists and any other  information  Employee has
reason to know  DIANON  would  like to treat as  confidential  for any  purpose.
Employee  agrees to keep  Confidential  Information  secret  whether  or not any
document containing such information is marked confidential.

     (3) All rights,  title and  interest in all  records,  documents,  or files
concerning the business of DIANON,  including, but not limited to, biomaterials,




processes,  letters,  trade  secrets,  laboratory  notebooks or other written or
electronically recorded material, whether or not produced by the Employee, shall
be and remain the  property  of DIANON.  Upon  termination  of  employment,  the
Employee shall not have the right to remove any such records from the offices of
DIANON. In addition,  Employee agrees to promptly return to DIANON all things of
whatsoever  nature that belong to DIANON,  and all records (in whatsoever  form,
format or medium) containing or related to Confidential Information of DIANON.

     (4) Employee  agrees to assign,  and does hereby  assign to DIANON,  all of
his/her  right,  title  and  interest  in and to all  inventions,  improvements,
discoveries or technical developments,  whether or not patentable,  which he/she
solely or jointly  with others,  may  conceive or reduce to practice  during the
term of his/her  employment (a) which are related in whole or in part,  directly
or indirectly,  to DIANON's product line, research and development,  or field of
technological or industrial specialization,  or (b) in the course of utilization
by DIANON of Employee's services in a technical or professional  capacity in the
areas  of  research,   development,   marketing,   management,   engineering  or
manufacturing,  or (c)  pursuant  to any  project of which  Employee is or was a
participant or member that is or was either  financed or directed by DIANON,  or
(d) at DIANON's expense, in whole or in part.

     (5)  Employee  agrees to  disclose  promptly to  DIANON's  Chief  Executive
Officer or his designee, all ideas,  discoveries,  and improvements conceived by
Employee  alone or in  collaboration  with others,  and to cooperate  fully with
DIANON both during and after  employment,  with  respect to the  procurement  of
patents for the  establishment  and  maintenance  of DIANON's or its  designee's
rights  and  interests  in  said   invention,   improvements,   discoveries   or
developments,  and to sign  all  papers  which  DIANON  may  deem  necessary  or
desirable for the purpose of vesting  DIANON or its designees  with such rights,
the expenses thereof to be paid by DIANON.

     (6) The  Employee  shall,  while  employed by DIANON,  devote  his/her best
efforts and his/her full time to the business of DIANON.

     (7) In the event of a breach or threatened breach of the provisions in this
Agreement, DIANON shall be entitled to an injunction restraining such breach, it
being  recognized that any injury arising from a breach would be irreparable and
would have no adequate  remedy at law; but nothing  herein shall be construed as
prohibiting  DIANON from pursuing any other remedy  available for such breach or
threatened  breach. In the event that Employee breaches or threatens a breach of
this Agreement,  DIANON shall be entitled to have its reasonable  legal fees and
costs paid by the  Employee  for any legal  services  relating  to the breach or
threatened breach.

     (8) This Agreement is not intended, and should not be construed in any way,
as a  contract  of  employment  for a  definite  period  of time or to  limit or
restrain   DIANON's  or  the  Employee's   right  to  terminate  the  employment
relationship at any time.





     (9) In the event any  provision or paragraph of this  Agreement is declared
to be invalid or unenforceable,  then the balance of this Agreement shall remain
in full force and effect.

     (10) This Agreement  shall be construed and enforced in accordance with the
laws of the State of Connecticut.

     (11) The  foregoing  contains  the entire  Agreement  between  the  parties
pertaining  to  non-competition   and  to  confidential   DIANON  documents  and
information.  No  modification  thereof shall be binding upon the parties unless
the same is in a writing  signed by the respective  parties.  This Agreement and
all of the terms and  conditions  contained  herein  shall  remain in full force
during the period of employment notwithstanding any change in compensation.

     (12) Employee  represents and warrants that he/she has no other  agreements
or  commitments  that  would  hinder  or  prevent  performance  of  his/her  job
responsibilities with DIANON. Unless authorized to do so, Employee agrees not to
disclose to DIANON or use in his/her  employment  with DIANON any  invention  or
confidential information belonging to any former employer or to any other person
other than DIANON.

     IN WITNESS WHEREOF,  the parties have entered into this Agreement as of the
date set forth above.


Employee:                              DIANON SYSTEMS, INC.


/S/  VERNON WELLS                      By:    /S/ KEVIN C. JOHNSON
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Date:  SEPT 3, 1997                    Date:  SEPTEMBER 3, 1997
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