EXHIBIT 10.4

                             EMPLOYMENT AGREEMENT



      THIS IS AN EMPLOYMENT  AGREEMENT  ("Agreement") made and entered into as
of the 1st day of May, 1999, by and between DIANON  Systems,  Inc., a Delaware
corporation ("DIANON"), and Ralph M. Richart, M.D. ("Richart").

                                  RECITALS:

      WHEREAS,  DIANON has acquired substantially all of the assets and business
of Kyto  Meridien  Diagnostics,  L.L.C.,  a New York limited  liability  company
("Kyto Meridien"), pursuant to the terms of an Asset Purchase Agreement dated as
of April 7, 1999, by and among DIANON,  Kyto Meridien,  Kyto Diagnostics,  L.P.,
Meridien  Diagnostics  Labs,  Inc.,  Richart  and A. Bruce  Shapiro  (the "Asset
Purchase Agreement"); and

      WHEREAS,  DIANON desires to employ  Richart for a period  commencing as of
the Closing Date  ("Closing  Date") of the Asset  Purchase  Agreement and ending
three  years  from that date and  Richart  desires  to work for  DIANON for such
period on the terms and conditions hereinafter provided; and

      WHEREAS, Richart's position with Kyto Meridien has given him access to and
familiarity  with the  confidential  information  and business of Kyto  Meridien
acquired  by DIANON and his  employment  with DIANON will give him access to and
familiarity with the confidential information and business of DIANON; and

      WHEREAS, DIANON would be irreparably harmed if Richart should disclose any
of the confidential  information  which Richart has acquired and will acquire or
by entering  into any  activity  competing  with DIANON or the  business of Kyto
Meridien acquired by DIANON.

      NOW,  THEREFORE,  in  consideration  of the  mutual  covenants,  terms and
conditions of this Agreement, Richart and DIANON agree as follows:

      1.    EMPLOYMENT.  DIANON  hereby  employs  Richart  for the  term of this
Agreement as specified in Section 3, below.  Richart's duties shall include: (i)
service,  for a period of one year from and after the Closing Date, as statutory
Laboratory  Director  at the  laboratory  facility  acquired by DIANON from Kyto
Meridien located at 216 Congers Road in New City, New York,  provided,  however,
that Richart's  responsibilities  in that regard shall be no greater in terms of
quantity  or  substance  than  those held at Kyto  Meridien  during the one year
period immediately preceding the Closing Date and provided further that he shall
not, except to the extent required by law or regulation, have responsibility for
the day-to-day  oversight or management of the laboratory;  (ii) for a period of
at least six months from and after the Closing Date,  performance of a volume of
surgical  and  anatomic  pathology  and  cytology   examinations  and  diagnoses
consistent with his workload while employed by Kyto Meridien and, thereafter, at
a reduced volume as mutually agreed; (iii) while serving as Laboratory Director,
performance of all requirements of a laboratory  director  specified under CLIA,
New  York  State  law and  other  federal,  state  and  local  laws,  rules  and
regulations;  (iv)  occasional  rendering of decisions  on  significant  medical
matters  and other  matters  materially  impacting  on  medical  decisions;  (v)




rendering,  as needed,  professional  advice to clients,  as well as written and
telephonic responses to client inquiries regarding test results or other medical
inquiries;  (vi) preparing client  communications and newsletters on medical and
laboratory  issues;  (vii) upon mutual  agreement,  attendance  and  delivery of
presentations   at   professional   meetings   and   conferences   as   DIANON's
representative;  and (vii) such other tasks and  assignments  that are  mutually
agreed to at the request of the senior management of DIANON.

      It is  expressly  agreed and  understood  that the above  duties  shall be
performed  by Richart on a good faith basis  subject to an  academic  and travel
schedule  commensurate  with his schedule in the one year immediately  preceding
the Closing Date.  Under no  circumstances  shall the  performance of any duties
herein  exceed  those  performed  by  Richart  during  the one year  immediately
preceding  the Closing Date in quantity or  substance  and,  further,  except as
required by law or  regulation,  such  performance  does not  require  Richart's
on-site  presence  other than on an incidental  basis.  DIANON further agrees to
make reasonable efforts to ensure that, during the term of this Agreement, there
will be  adequate  personnel  and  consultants  available  to assist and support
Richart in the performance of his duties hereunder.

      During his  employment  Richart  shall at all times  conduct  himself  and
perform his professional  services in a proficient and professional  manner,  in
accordance  with the applicable  standards of care and the highest  standards of
ethics of the medical profession.

      2.    COMPENSATION.  As full  consideration  for the services  rendered by
Richart  pursuant  to  this  Agreement,  together  with  Richart's  undertakings
pertaining to the  preservation of confidential  information and the restrictive
covenant  set forth,  respectively,  in  Sections 4 and 5 below,  DIANON  shall,
during the term of this Agreement, compensate Richart as follows:

            (a)   DIANON  shall pay Richart an annualized  salary of two hundred
thousand ($200,000) dollars, payable in twenty-six equal biweekly (one every two
weeks)  increments,  of  seven  thousand  six  hundred  ninety-two  dollars  and
thirty-one cents ($7,692.31);

            (b)   DIANON  shall  reimburse the reasonable  business  expenses of
Richart in  performing  his duties  hereunder in  accordance  with such policies
regarding  employee  expenses  as DIANON  may have in  effect  from time to time
during the term;

            (c)   DIANON shall provide  Richart with an  automobile  allowance
of five hundred and sixty-nine ($569) dollars per month;

            (d)   Richart  shall be eligible for such other employee benefits as
are  generally  provided  by DIANON to its  employees  subject  to the terms and
conditions, including eligibility conditions, of any applicable employee benefit
plan or program;  provided that,  during the period of employee  conversion,  as
determined by DIANON  consistent  with the  requirements  of the Asset  Purchase
Agreement,  Richart  shall be entitled to such Kyto  Meridien  benefits that are
required by the Asset  Purchase  Agreement  to be extended to all Kyto  Meridien
employees hired by DIANON.

            (e)   Upon  termination of employment,  Richart may, at his own cost
and in accordance with the requirements of COBRA,  extend his employee insurance
benefits.


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      3.    TERM.   Unless sooner terminated in accordance with Section 9 below,
the term of this  Agreement  and  Richart's  employment  shall  commence  on the
Closing Date of the Asset  Purchase  Agreement and end on the third  anniversary
thereof.

      4.    CONFIDENTIAL  INFORMATION.  From and after the date hereof,  Richart
will not,  directly  or  indirectly,  use for his own  benefit or  purposes,  or
disclose  to, or use for the  benefit or  purpose of any person or entity  other
than DIANON,  any  confidential  information,  knowledge or data relating to the
business or operations of DIANON or those acquired by DIANON from Kyto Meridien.
Such information,  knowledge or data includes,  but is not limited to, secret or
confidential  matters not published or generally known in the industry,  such as
information regarding pricing, costs, purchasing,  profits, financing,  markets,
sales  or  customer  lists,   future   developments,   audits,   investigations,
enforcement actions, regulatory compliance,  laboratory procedures and marketing
and expansion  plans.  Any and all materials which may be produced or created by
Richart or others,  or which may come into his  possession  in the course of his
employment,  or which  relate  in any  manner  to the  business  or  prospective
business of DIANON are and shall be the exclusive property of DIANON and Richart
shall  not have  any  right,  title or  interest  in any  such  materials.  Upon
termination  of his  employment,  Richart shall not have the right to remove any
such materials  from the offices of DIANON and shall  promptly  return to DIANON
all things of whatever nature that belong to DIANON, including all materials and
records in any form,  format or medium containing or related to the confidential
information  of DIANON,  and he shall  neither  make nor retain any part or copy
thereof for his personal use or the use of third parties.

            Notwithstanding  the foregoing,  confidential  information shall not
include any information  that is: (i)  demonstrably  developed  independently by
Richart;  (ii)  publicly  disclosed by DIANON or otherwise in the public  domain
without violation of this Agreement by Richart;  or (iii) rightfully received by
Richart from a third party, which, by disclosing to Richart, does not breach any
obligation or duty to DIANON.  Notwithstanding  this Section 4, Richart may make
such  disclosures  of  confidential  information  as are duly compelled by court
order or as required by law.

      5.    RESTRICTIVE  COVENANT.  In  consideration  of this Agreement and the
purchase of the assets and business of Kyto Meridien by DIANON,  for a period of
three  years  from and  after the  Closing  Date and for any  renewal  period or
extension of the term hereof,  and  notwithstanding  any earlier  termination of
this Agreement, except upon the express written consent of DIANON (which consent
may be unreasonably withheld), Richart shall not, for his own account, on behalf
of, or jointly with,  any other person,  directly or  indirectly,  own,  manage,
operate,  join,  control,  finance,  invest in, perform services for, advise (or
advise  others with respect to), or  otherwise  participate  in, or be connected
with,  or  become  or act as a  partner,  manager,  member,  director,  officer,
employee,  consultant,  representative  or agent  of any  business  (other  than
DIANON), individual,  partnership, firm, proprietorship,  professional practice,
corporation,  limited  liability  company or other entity that provides clinical
laboratory or anatomic or surgical  pathology  services within a one hundred and
fifty mile radius of New York City; provided however,  that Richart may purchase
or own,  solely as an inactive  investor,  the securities of any entity that are
publicly  traded on a national  securities  exchange where  Richart's  aggregate
holdings of such  securities do not exceed two percent of the voting power or of
any class of stock of such entity.


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      Notwithstanding anything to the contrary herein, Richart may continue: (i)
in his academic post at the Columbia College of Physicians and Surgeons; (ii) in
his  position  as  the  Associate  Director  of  Obstetrical  and  Gynecological
Pathology and Cytology at Columbia  Presbyterian  Medical  Center;  and (iii) to
participate,  from time to time,  as a consultant  in research  studies (but not
clinical  trials)  relating to clinical and surgical  pathology,  provided  that
Richart  shall not act as a  consultant  in  research  studies  for any  medical
laboratory.

            In addition to the foregoing,  during the same three-year period and
for any renewal  period or extension of the term hereof,  Richart  shall not, on
his own  behalf,  or on behalf of any other  person or entity:  (i)  solicit the
customers,  suppliers  or  employees of DIANON or any  affiliated  entity;  (ii)
solicit or seek to hire any  employee  of DIANON or any  affiliated  entity;  or
(iii) attempt in any manner,  directly or  indirectly,  to influence,  induce or
encourage any such employee to leave the  employment of DIANON or any affiliated
entity.  Richart shall not take any action intended,  or which may reasonably be
expected,  directly or  indirectly,  to impair the goodwill,  reputation or good
name of DIANON or Kyto Meridien, or otherwise to be detrimental to the interests
of DIANON,  including any action intended,  or which may reasonably be expected,
directly or indirectly to benefit a competitor of DIANON.

      6.    SCOPE  OF  RESTRICTIONS.  Richart agrees that the  restrictions  set
forth in Section 5 are  reasonable.  If,  however,  a court  determines that any
provision of Section 5 is unreasonable,  either in geographic  scope,  length of
time or  otherwise,  then  Section 5 shall be  interpreted  and  enforced to the
maximum extent  permitted by law and Richart consents and agrees that such scope
may be judicially modified accordingly in any proceeding brought to enforce such
restriction.

      7.    INJUNCTIVE  RELIEF. Richart acknowledges that irreparable harm would
be suffered by DIANON in the event that any of the provisions of Sections 4 or 5
were not performed fully in accordance with the terms specified therein and that
monetary  damages are an  inadequate  remedy for breach  thereof  because of the
difficulty of  ascertaining  and  quantifying  the amount of damage that will be
suffered  by DIANON in the event  that such  undertakings  and  provisions  were
breached or violated. Accordingly,  Richart agrees that DIANON shall be entitled
to an  injunction or  injunctions  to restrain,  enjoin and prevent  breaches or
threatened  breaches of the  covenants,  undertakings  and  provisions  of those
sections and to enforce  specifically the provisions therein in any court of the
United  States  or any  state  having  jurisdiction  over the  matter,  it being
understood  that any such remedies  shall be in addition to, and not in lieu of,
any other  rights and  remedies  available  at law or in equity and shall not be
deemed  exclusive of any common law or other rights of DIANON in connection with
the matters covered hereby.

      8.    INTELLECTUAL  PROPERTY RIGHTS.  Richart agrees to assign, and hereby
does  assign to  DIANON  all of his  right,  title  and  interest  in and to all
inventions, improvements, discoveries and technical developments, whether or not
patentable,  which he solely or jointly with  others,  may conceive or reduce to
practice  during the term of his employment,  which are related,  in whole or in
part, directly or indirectly, to the business of, or services or products of the
type, provided by DIANON, or which may reasonably be provided or used by DIANON,
or which are otherwise developed, in whole or in part, at DIANON's expense.

      Richart shall disclose promptly to DIANON's Chief Executive  Officer,  all
such  ideas,   discoveries  and  improvements  conceived  by  him  alone  or  in
collaboration with others, and shall 


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cooperate  fully with DIANON both during and after  employment,  with respect to
the  procurement of patents for the  establishment  and  maintenance of DIANON's
rights  and  interests  in  said   inventions,   improvements,   discoveries  or
developments,  and shall  sign all  papers  which  DIANON  may  reasonably  deem
necessary or desirable for the purpose of vesting it with such rights.

      9.    TERMINATION.      (a) Richart's  employment  under this  Agreement
shall terminate on the occurrence of any of the following events:

            (i)   Upon the  disqualification  of Richart to practice  medicine
in the State of New York;

            (ii)  Upon  the  disqualification  of  Richart,  or his  failure  to
maintain all  necessary  licenses and  certifications,  to serve as a laboratory
director in the State of New York,  while  serving as a Laboratory  Director for
DIANON;

            (iii) Upon the death of Richart;

            (iv)  Upon  the passage of thirty (30) days after written  notice of
termination without cause from DIANON to Richart;

            (v)   Upon  the sending of written notice from DIANON describing the
activities  constituting an act of default falling within any one or more of the
following categories:

                  (A)   Richart's  breach of any  material  promise or agreement
                        set forth herein, including,  without limitation,  those
                        set forth in  Sections  4, 5 and 8 above,  or failure to
                        perform  substantially  all  of  the  duties  reasonably
                        required by Section 1; or

                  (B)   Richart's  commission  of an act of gross  negligence or
                        willful  misconduct in the  performance of his duties or
                        obligations  hereunder  or an act of  negligence  in the
                        performance of a medical function;

Provided  that no such  termination  under  this  subsection  9(a)(v)  shall  be
effective  unless  Richart has first been afforded an opportunity to correct the
alleged  default,  but such default  continues,  recurs or can not  otherwise be
corrected,  in the good faith  judgment  of  DIANON,  within  thirty  days after
delivery of such written notice of default to Richart; and

            (vi)  Upon  the  occurrence of an event or the  commission of an act
under  which  Richart  is or may  become  subject  to  mandatory  or  permissive
exclusion  from  Medicare and State health care  programs,  including  those set
forth  in  sections  1128,  1156  and 1892 of the  Social  security  Act and any
regulations promulgated thereunder.

      (b)   In  the  event  of a  termination  of  this  Agreement  pursuant  to
subsections  9(a)(iii)  or  9(a)(iv)  above,  DIANON  shall  continue to pay the
compensation  required  by  subsections  2(a) and 2(c)  above  until  the  third
anniversary of the Closing Date of the Asset Purchase Agreement.


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      (c)   Sections  4, 5, 6, 7,  11,  13 and 14 of this  Agreement  shall,  in
accordance  with their terms,  survive any  termination  or  expiration  of this
Agreement,  whether any such  termination be with or without cause or expiration
occurs  with  the  passage  of  time.  Without  limitation,  no  termination  or
expiration of this Agreement  shall relieve Richart of his obligations to DIANON
with respect to the  restrictive  covenant in Section 5 and the  preservation of
confidential  information  under  Section 4. Should  Richart  violate any of the
requirements  of Sections 4 or 5 of this  Agreement,  DIANON may, in addition to
any other remedies  provided to DIANON under this Agreement,  the Asset Purchase
Agreement,   at  law  or  in   equity,   immediately   terminate   any   further
post-termination  payments to Richart  hereunder  that  otherwise  may have been
required.

      10.   WAIVER.  The  failure  of  either  party  at  any  time  to  require
performance  by the other party of any provision  hereof shall not affect in any
way the full right to require such performance at any time thereafter, nor shall
a waiver by either party of a breach of any provision hereof be taken or held to
be a waiver of the provision itself.

      11.   NOTICES.  All notices,  requests,  demands and other  communications
hereunder  shall be in  writing  and shall be deemed to have been duly  given if
delivered by hand, by  nationally  recognized  overnight  delivery  service,  or
mailed by  certified or  registered  mail,  postage  prepaid,  and  addressed as
follows:

            If to Richart:    Ralph M. Richart, M.D.
                              350 Shore Drive
                              Oakdale, New York  11769

            with a copy to:   Brown Raysman  Millstein  Felder & Steiner LLP
                              120 West 45th Street
                              New York, New York 10036
                              Attn: Sarah Hewitt, Esq.




            If to DIANON:     DIANON Systems, Inc.
                              200 Watson Boulevard
                              Stratford, Connecticut  06497
                              Attn: President


      12.   ENTIRE  AGREEMENT.  This Agreement and the Asset Purchase  Agreement
set forth the entire agreement and  understanding of the parties  concerning the
subject  matter  hereof.  This  Agreement  may  be  amended  only  by a  written
instrument signed by both parties, which instrument must make specific reference
to this Agreement and the intention to modify it.

      13.   GOVERNING  LAW. This Agreement shall be governed by and construed in
accordance  with the laws of the  State of New  York  without  reference  to the
conflicts of laws provisions of that state.

      14.   INDEMNIFICATION.  DIANON shall  protect,  defend,  hold harmless and
indemnify  Richart  from  and  against  all  losses,  claims,   actions,  suits,
proceedings,   investigations,  


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demands,  liabilities,  judgments,  settlements,  damages,  costs  and  expenses
(including  reasonable  legal  fees and  costs)  which are  asserted  against or
incurred by Richart as a result of, or which arise out of, Richart's performance
of his duties within the scope of his employment with DIANON,  all in accordance
with the May 15, 1997 resolution of the DIANON Board of Directors  pertaining to
indemnification  of  physicians  employed  by it, a copy of  which  is  attached
hereto.

      IN WITNESS WHEREOF, the parties have executed this Agreement as of the day
first above written.


                                          /s/ Ralph M. Richart
                                          --------------------
                                          Ralph M. Richart, M.D.


                                          DIANON SYSTEMS, INC.


                                          /s/ Kevin J. Johnson
                                          --------------------
                                          By:  Kevin J. Johnson
                                          Its:   President & CEO




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