As filed with the Securities and Exchange Commission on April 5, 2000

                                                      REGISTRATION NO.
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                 ---------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      under
                          THE SECURITIES ACT OF 1933

                                 ---------------

                              DIANON SYSTEMS, INC.
             (Exact name of registrant as specified in its charter)

           DELAWARE                                              06-1128081
(State or other jurisdiction of                               (I.R.S. Employer
       incorporation or                                      Identification No.)
         organization)
                              200 Watson Boulevard
                               Stratford, CN 06615
                                 (203) 381-4000
          (Address, including Zip Code, of principal executive offices)

                                 ---------------

                              DIANON SYSTEMS, INC.
                            1999 STOCK INCENTIVE PLAN

                            (Full title of the Plan)

                                 ---------------
                              Mr. Kevin C. Johnson
                      President and Chief Executive Officer
                              Dianon Systems, Inc.
                              200 Watson Boulevard
                               Stratford, CT 06615
                                 (203) 381-4000

                                    Copy to:

                            Dennis J. Block, Esq.
                          Cadwalader, Wickersham & Taft
                                 100 Maiden Lane
                            New York, New York 10038
                                 (212) 504-6000

  (Name and address, including Zip Code, telephone number and area code, of
                              agent for service)

                                 ---------------


<TABLE>
                                    CALCULATION OF REGISTRATION FEE
<CAPTION>
============================ ===================== ======================= ====================== ====================
 Title of Securities to be       Amount to be         Proposed Maximum       Proposed Maximum          Amount of
        Registered              Registered(1)             Offering          Aggregate Offering       Registration
                                                     Price Per Share (2)         Price (2)                Fee
---------------------------- --------------------- ----------------------- ---------------------- --------------------
<S>                             <C>                        <C>                  <C>                    <C>
  Common Stock, $0.01 par       300,000 shares             $19.1875             $5,756,250             $1,519.65
           value
============================ ===================== ======================= ====================== ====================
</TABLE>

(1)  Based on the number of shares of common stock of Dianon Systems, Inc. (the
     "Company") reserved for issuance upon exercise of options granted pursuant
     to the Dianon Systems, Inc. 1999 Stock Incentive Plan (the "Plan"). In
     addition to such shares, this registration statement also covers an
     undetermined number of shares of common stock of the Company that, by
     reason of certain events specified in the Plan, may become issuable upon
     exercise of options through the application of certain anti-dilution
     provisions.

(2)  Estimated solely for purpose of calculating the registration fee in
     accordance with Rule 457 of the Securities Act of 1933, pursuant to which
     shares subject to outstanding options are deemed to be offered at the
     prices at which such options may be exercised and restricted shares and
     shares that may be acquired upon exercise of options granted in the future
     are deemed to be offered at $19.1875 per share, the average of the daily
     high and low sales prices of common stock of the Company on the Nasdaq
     National Market at the close of trading on March 29, 2000.

<PAGE>

                                     PART I

             INFORMATION REQUIRED IN THE SECTION 10(A) PROSPECTUS

ITEM 1.     PLAN INFORMATION.

            Not required to be filed with the Securities and Exchange Commission
(the "Commission").

ITEM 2.     REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION.

            Not required to be filed with the Commission.

            Note: The document containing the information specified in this Part
I will be sent or given to employees as specified by Rule 428(b)(1) under the
Securities Act of 1933, as amended (the "Securities Act"). Such document need
not be filed with the Commission either as part of this registration statement
or as prospectuses or prospectus supplements pursuant to Rule 424 under the
Securities Act. These documents and the documents incorporated by reference in
this registration statement pursuant to Item 3 of Part II of this form, taken
together, constitute a prospectus that meets the requirements of Section 10(a)
of the Securities Act.

                                     PART II

ITEM 3.     INCORPORATION OF DOCUMENTS BY REFERENCE.

            The following documents, which have been filed by the Company with
the Commission, are incorporated in the Registration Statement by reference:

      (1)   the Company's Annual Report on Form 10-K for the fiscal year ended
            December 31, 1999, which was filed with the Commission pursuant to
            the Securities Exchange Act of 1934, as amended (the "Exchange
            Act"), and the exhibits therein;

      (2)   the description of the Company's Common Stock (the "Common Stock")
            contained in the Company's Registration Statement on Form 8-A, dated
            November 8, 1995;

      (3)   the amendment to the Company's registration statement on Form S-1/A,
            dated July 30, 1991;

      (4)   the amendment to the Company's registration statement on Form S-1/A,
            dated July 23, 1991;

      (5)   the amendment to the Company's registration statement on Form S-1/A,
            dated July 18, 1991;

      (6)   the Company's  registration  statement on Form S-1, dated June 14,
            1991 (Registration No. 33-41226).

All documents filed by the Company pursuant to Sections 13(a), 13(c), 14 and
15(d) of the Exchange Act after the end of the fiscal year ended December 31,
1999 and prior to the date of the termination of the offering of the Common
Stock offered hereby shall be deemed to be incorporated by reference into this
registration statement and to be a part hereof from the date of filing of such
documents. Any statement contained herein or in a document incorporated or
deemed to be incorporated by reference herein shall be deemed to be modified or
superseded for purposes of this registration statement to the extent that a
statement contained herein or in any document which is or is deemed to be
incorporated by reference herein modifies or supersedes such statement. Any
statement so modified or superseded shall not be deemed, except as so modified
or superseded, to constitute a part of this registration statement.

            Dianon  Systems,  Inc. will provide  without charge to each person
to whom this Prospectus is delivered,  upon request of any such person, a copy
of any or all of the  foregoing  documents  incorporated  herein by  reference
(other than exhibits to such  documents).  Written requests should be directed
to Dianon  Systems,  Inc.  Attn:  David  Schreiber,  Senior Vice President and
Chief  Financial  Officer,  at 200  Watson  Boulevard,  Stratford,  CT  06615.
Telephone requests may be directed to (203) 381-4055.

ITEM 4.     DESCRIPTION OF SECURITIES.

            Not applicable.

ITEM 5.     INTERESTS OF NAMED EXPERTS AND COUNSEL.

            Not applicable.

ITEM 6.     INDEMNIFICATION OF DIRECTORS AND OFFICERS.

            Subsection (a) of Section 145 of the General Corporation Law of
Delaware (the "DGCL") empowers a corporation to indemnify any person who was or
is a party or is threatened to be made a party to any threatened, pending or
complete action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he is or was a director, employee or agent of the
corporation or is or was serving at the request of the corporation as a
director, officer, employee or agent of another corporation, partnership, joint
venture, trust or other enterprise, against expenses (including attorneys'
fees), judgments, fines and amounts paid in settlement actually and reasonably
incurred by him in connection with such action, suit or proceeding if he acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the corporation and, with respect to any criminal action
or proceeding, had no cause to believe his conduct was unlawful.

            Subsection (b) of Section 145 of the DGCL empowers a corporation to
indemnify any person who was or is a party or is threatened to be made a party
to any threatened, pending or completed action or suit by or in the right of the
corporation to procure a judgment in its favor by reason of the fact that such
person acted in any of the capacities set forth above, against expenses
(including attorneys' fees) actually and reasonably incurred by him in
connection with the defense or settlement of such action or suit if he acted in
good faith and in a manner he reasonably believed to be in or not opposed to the
best interests of the corporation and except that no indemnification may be made
in respect to any claim, issue or matter as to which such person shall have been
adjudged to be liable to the corporation unless and only to the extent that the
Court of Chancery or the court in which such action or suit was brought shall
determine that despite the adjudication of liability such person is fairly and
reasonably entitled to indemnity for such expenses which the court shall deem
proper.

            Section 145 of the DGCL further provides that to the extent a
director, officer, employee or agent of a corporation has been successful in the
defense of any action, suit or proceeding referred to in subsections (a) and (b)
or in the defense of any claim, issue or matter therein, he shall be indemnified
against expenses (including attorneys' fees) actually and reasonably incurred by
him in connection therewith; that indemnification or advancement of expenses
provided for by Section 145 shall not be deemed exclusive of any other rights to
which the indemnified party may be entitled; and empowers the corporation to
purchase and maintain insurance on behalf of a director, officer, employee or
agent of the corporation against any liability asserted against him or incurred
by him in any such capacity or arising out of his status as such whether or not
the corporation would have the power to indemnify him against such liabilities
under Section 145.

            Article X of the Company's Certificate of Incorporation provides
that a director shall not be personally liable to the Company or its
stockholders for damages for breach of fiduciary duty as a director, except for
liability (i) for any breach of the director's duty of loyalty to the
Corporation or its stockholders, (ii) for acts or omissions not in good faith or
which involve intentional misconduct or a knowing violation of law, (iii) under
Section 174 of the Delaware General Corporation Law, or (iv) for any transaction
from which the director derived an improper personal benefit.

             Article X of the Company's Certificate of Incorporation requires
the Company, among other things, to indemnify to the fullest extent permitted by
the DGCL, any person who is or was or has agreed to become a director or officer
of the Company, who was or is made a party to, or is threatened to be made a
party to, or has become a witness in, any threatened, pending or completed
action, suit or proceeding, including actions or suits by or in the right of the
Company, by reason of such agreement or service or the fact that such person is,
was or has agreed to serve as a director, officer, employee or agent of another
corporation or organization at the written request of the Company.

ITEM 7.     EXEMPTION FROM REGISTRATION CLAIMED.

            Not applicable.

ITEM 8.     EXHIBITS.

            4.1   Dianon Systems, Inc. 1999 Stock Incentive Plan, incorporated
                  by reference to Exhibit 99.B to the Company's Proxy Statement
                  on Schedule 14A, dated October 21, 1999.

            4.2   Certificate of Incorporation of the Company, incorporated by
                  reference to the Company's Registration Statement on Form S-1,
                  dated June 14, 1991 (Registration No. 33-41226).

            4.3   Bylaws of Company, incorporated by reference to the Exhibit
                  3.3. to the Company's Quarterly Report on Form 10-Q, dated
                  November 14, 1997.

            5.1   Opinion of Cadwalader, Wickersham & Taft, counsel for Company,
                  as to the legality of the securities being registered.

            23.1  Consent of Cadwalader, Wickersham & Taft (included in Exhibit
                  5.1 hereof).

            23.2  Consent of Arthur Anderson LLP.

ITEM 9.     UNDERTAKINGS.

      A. Rule 415 offering. The Company hereby undertakes:

            (1) To file, during any period in which offers or sales are being
made, a post-effective amendment to this registration statement:

                  (i) To include any prospectus required by Section 10(a)(3) of
the Securities Act;

                  (ii) To reflect in the prospectus any facts or events arising
after the effective date of the registration statement (or the most recent
post-effective amendment thereof) which, individually or in the aggregate,
represent a fundamental change in the information set forth in the registration
statement; and

                  (iii) To include any material information with respect to the
plan of distribution not previously disclosed in the registration statement or
any material change to such information in the registration statement;

                  Provided, however, that the undertakings in paragraphs
(a)(1)(i) and (a)(1)(ii) do not apply if the information required to be included
in a post-effective amendment by those paragraphs is contained in periodic
reports filed by the Company pursuant to Section 13 or 15(d) of the Exchange Act
that are incorporated by reference in the registration statement.

            (2) That, for the purpose of determining liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

            (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

      B. Filings incorporating subsequent Exchange Act documents by reference.
The Company hereby undertakes that, for purposes of determining any liability
under the Securities Act, each filing of the Company's annual report pursuant to
Section 13(a) or 15(d) of the Exchange Act (and, where applicable, each filing
of an employee benefit plan's annual report pursuant to Section 15(d) of the
Exchange Act) that is incorporated by reference in the registration statement
shall be deemed to be a new registration statement relating to the securities
offered therein and the offering of such securities at that time shall be deemed
to be the initial bona fide offering thereof.

      C. Incorporated annual and quarterly reports. The Company hereby
undertakes to deliver or cause to be delivered with the prospectus, to each
person to whom the prospectus is sent or given, the latest annual report to
security holders that is incorporated by reference in the prospectus and
furnished pursuant to and meeting the requirements of Rule 14a-3 or Rule 14c-3
under the Securities Exchange Act of 1934; and, where interim financial
information required to be presented by Article 3 of Regulation S-X is not set
forth in the prospectus, to deliver, or cause to be delivered to each person to
whom the prospectus is sent or given, the latest quarterly report that is
specifically incorporated by reference in the prospectus to provide such interim
financial information.

      D. Filing of registration on Form S-8. Insofar as indemnification for
liabilities arising under the Securities Act may be permitted to directors,
officers and controlling persons of the Company pursuant to the foregoing
provisions, or otherwise, the Company has been advised that in the opinion of
the Commission such indemnification is against public policy as expressed in the
Securities Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the Company
for expenses incurred or paid by a director, officer or controlling person of
the Company in the successful defense of any action, suit or proceeding) is
asserted by such director, officer or controlling person in connection with the
securities being registered, the Company will, unless in the opinion of its
counsel the matter has been settled by controlling precedent, submit to a court
of appropriate jurisdiction the question whether such indemnification by it is
against public policy as expressed in the Securities Act and will be governed by
the final adjudication of such issue.

<PAGE>

                                   SIGNATURES

            Pursuant to the requirements of the Securities Act, the Company
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the State of Connecticut on March 31, 2000.

                                       DIANON SYSTEMS, INC.
                                          (Registrant)

                                       By:  /S/ Kevin C. Johnson
                                           -------------------------------------
                                           Kevin C. Johnson
                                           President and Chief Executive Officer

            Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

          SIGNATURE                         TITLE                     DATE
          ---------                         -----                     ----

/s/ Kevin C. Johnson          President, Chief Executive        March 31, 2000
---------------------------   Officer and Director
Kevin C. Johnson



/s/ David R. Schreiber        Chief Financial Officer and       March 31, 2000
---------------------------   Director (Chief Financial
David R.  Schreiber           Officer and Corporate
                              Secretary)



/s/ John P. Davis             Director                          March 31, 2000
---------------------------
John P. Davis



/s/ Bruce K. Crowther         Director                          March 31, 2000
---------------------------
Bruce K. Crowther



/s/ Timothy Geary             Director                          March 31, 2000
---------------------------
E. Timothy Geary



/s/ G.S. Beckwith Gilbert     Director                          March 31, 2000
---------------------------
G.S. Beckwith Gilbert


                              Director                          March 31, 2000
---------------------------
Jeffrey L. Sklar
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As filed with the Securities and Exchange Commission on April 5, 2000

                                                      REGISTRATION NO.
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                 ---------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      under
                          THE SECURITIES ACT OF 1933

                                 ---------------

                              DIANON SYSTEMS, INC.
             (Exact name of registrant as specified in its charter)

           DELAWARE                                              06-1128081
(State or other jurisdiction of                               (I.R.S. Employer
       incorporation or                                      Identification No.)
         organization)
                              200 Watson Boulevard
                               Stratford, CN 06615
                                 (203) 381-4000
          (Address, including Zip Code, of principal executive offices)

                                 ---------------

                              DIANON SYSTEMS, INC.
                            1999 STOCK INCENTIVE PLAN

                            (Full title of the Plan)

                                 ---------------
                              Mr. Kevin C. Johnson
                      President and Chief Executive Officer
                              Dianon Systems, Inc.
                              200 Watson Boulevard
                               Stratford, CT 06615
                                 (203) 381-4000

                                    Copy to:

                            Dennis J. Block, Esq.
                          Cadwalader, Wickersham & Taft
                                 100 Maiden Lane
                            New York, New York 10038
                                 (212) 504-6000

  (Name and address, including Zip Code, telephone number and area code, of
                              agent for service)

                                 ---------------

                                    CALCULATION OF REGISTRATION FEE
============================ ===================== ======================= ====================== ====================
 Title of Securities to be       Amount to be         Proposed Maximum       Proposed Maximum          Amount of
        Registered              Registered(1)             Offering          Aggregate Offering       Registration
                                                     Price Per Share (2)         Price (2)                Fee
---------------------------- --------------------- ----------------------- ---------------------- --------------------
Common Stock, $0.01 par       300,000 shares             $19.1875             $5,756,250             $1,519.65
           value
============================ ===================== ======================= ====================== ====================
(1)  Based on the number of shares of common stock of Dianon Systems, Inc. (the
     "Company") reserved for issuance upon exercise of options granted pursuant
     to the Dianon Systems, Inc. 1999 Stock Incentive Plan (the "Plan"). In
     addition to such shares, this registration statement also covers an
     undetermined number of shares of common stock of the Company that, by
     reason of certain events specified in the Plan, may become issuable upon
     exercise of options through the application of certain anti-dilution
     provisions.

(2)  Estimated solely for purpose of calculating the registration fee in
     accordance with Rule 457 of the Securities Act of 1933, pursuant to which
     shares subject to outstanding options are deemed to be offered at the
     prices at which such options may be exercised and restricted shares and
     shares that may be acquired upon exercise of options granted in the future
     are deemed to be offered at $19.1875 per share, the average of the daily
     high and low sales prices of common stock of the Company on the Nasdaq
     National Market at the close of trading on March 29, 2000.
PART I

             INFORMATION REQUIRED IN THE SECTION 10(A) PROSPECTUS

ITEM 1.     PLAN INFORMATION.

            Not required to be filed with the Securities and Exchange Commission
(the "Commission").

ITEM 2.     REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION.

            Not required to be filed with the Commission.

            Note: The document containing the information specified in this Part
I will be sent or given to employees as specified by Rule 428(b)(1) under the
Securities Act of 1933, as amended (the "Securities Act"). Such document need
not be filed with the Commission either as part of this registration statement
or as prospectuses or prospectus supplements pursuant to Rule 424 under the
Securities Act. These documents and the documents incorporated by reference in
this registration statement pursuant to Item 3 of Part II of this form, taken
together, constitute a prospectus that meets the requirements of Section 10(a)
of the Securities Act.

                                     PART II

ITEM 3.     INCORPORATION OF DOCUMENTS BY REFERENCE.

            The following documents, which have been filed by the Company with
the Commission, are incorporated in the Registration Statement by reference:

      (1)   the Company's Annual Report on Form 10-K for the fiscal year ended
            December 31, 1999, which was filed with the Commission pursuant to
            the Securities Exchange Act of 1934, as amended (the "Exchange
            Act"), and the exhibits therein;

      (2)   the description of the Company's Common Stock (the "Common Stock")
            contained in the Company's Registration Statement on Form 8-A, dated
            November 8, 1995;

      (3)   the amendment to the Company's registration statement on Form S-1/A,
            dated July 30, 1991;

      (4)   the amendment to the Company's registration statement on Form S-1/A,
            dated July 23, 1991;

      (5)   the amendment to the Company's registration statement on Form S-1/A,
            dated July 18, 1991;

      (6)   the Company's  registration  statement on Form S-1, dated June 14,
            1991 (Registration No. 33-41226).

All documents filed by the Company pursuant to Sections 13(a), 13(c), 14 and
15(d) of the Exchange Act after the end of the fiscal year ended December 31,
1999 and prior to the date of the termination of the offering of the Common
Stock offered hereby shall be deemed to be incorporated by reference into this
registration statement and to be a part hereof from the date of filing of such
documents. Any statement contained herein or in a document incorporated or
deemed to be incorporated by reference herein shall be deemed to be modified or
superseded for purposes of this registration statement to the extent that a
statement contained herein or in any document which is or is deemed to be
incorporated by reference herein modifies or supersedes such statement. Any
statement so modified or superseded shall not be deemed, except as so modified
or superseded, to constitute a part of this registration statement.

            Dianon  Systems,  Inc. will provide  without charge to each person
to whom this Prospectus is delivered,  upon request of any such person, a copy
of any or all of the  foregoing  documents  incorporated  herein by  reference
(other than exhibits to such  documents).  Written requests should be directed
to Dianon  Systems,  Inc.  Attn:  David  Schreiber,  Senior Vice President and
Chief  Financial  Officer,  at 200  Watson  Boulevard,  Stratford,  CT  06615.
Telephone requests may be directed to (203) 381-4055.

ITEM 4.     DESCRIPTION OF SECURITIES.

            Not applicable.

ITEM 5.     INTERESTS OF NAMED EXPERTS AND COUNSEL.

            Not applicable.

ITEM 6.     INDEMNIFICATION OF DIRECTORS AND OFFICERS.

            Subsection (a) of Section 145 of the General Corporation Law of
Delaware (the "DGCL") empowers a corporation to indemnify any person who was or
is a party or is threatened to be made a party to any threatened, pending or
complete action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he is or was a director, employee or agent of the
corporation or is or was serving at the request of the corporation as a
director, officer, employee or agent of another corporation, partnership, joint
venture, trust or other enterprise, against expenses (including attorneys'
fees), judgments, fines and amounts paid in settlement actually and reasonably
incurred by him in connection with such action, suit or proceeding if he acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the corporation and, with respect to any criminal action
or proceeding, had no cause to believe his conduct was unlawful.

            Subsection (b) of Section 145 of the DGCL empowers a corporation to
indemnify any person who was or is a party or is threatened to be made a party
to any threatened, pending or completed action or suit by or in the right of the
corporation to procure a judgment in its favor by reason of the fact that such
person acted in any of the capacities set forth above, against expenses
(including attorneys' fees) actually and reasonably incurred by him in
connection with the defense or settlement of such action or suit if he acted in
good faith and in a manner he reasonably believed to be in or not opposed to the
best interests of the corporation and except that no indemnification may be made
in respect to any claim, issue or matter as to which such person shall have been
adjudged to be liable to the corporation unless and only to the extent that the
Court of Chancery or the court in which such action or suit was brought shall
determine that despite the adjudication of liability such person is fairly and
reasonably entitled to indemnity for such expenses which the court shall deem
proper.

            Section 145 of the DGCL further provides that to the extent a
director, officer, employee or agent of a corporation has been successful in the
defense of any action, suit or proceeding referred to in subsections (a) and (b)
or in the defense of any claim, issue or matter therein, he shall be indemnified
against expenses (including attorneys' fees) actually and reasonably incurred by
him in connection therewith; that indemnification or advancement of expenses
provided for by Section 145 shall not be deemed exclusive of any other rights to
which the indemnified party may be entitled; and empowers the corporation to
purchase and maintain insurance on behalf of a director, officer, employee or
agent of the corporation against any liability asserted against him or incurred
by him in any such capacity or arising out of his status as such whether or not
the corporation would have the power to indemnify him against such liabilities
under Section 145.

            Article X of the Company's Certificate of Incorporation provides
that a director shall not be personally liable to the Company or its
stockholders for damages for breach of fiduciary duty as a director, except for
liability (i) for any breach of the director's duty of loyalty to the
Corporation or its stockholders, (ii) for acts or omissions not in good faith or
which involve intentional misconduct or a knowing violation of law, (iii) under
Section 174 of the Delaware General Corporation Law, or (iv) for any transaction
from which the director derived an improper personal benefit.

             Article X of the Company's Certificate of Incorporation requires
the Company, among other things, to indemnify to the fullest extent permitted by
the DGCL, any person who is or was or has agreed to become a director or officer
of the Company, who was or is made a party to, or is threatened to be made a
party to, or has become a witness in, any threatened, pending or completed
action, suit or proceeding, including actions or suits by or in the right of the
Company, by reason of such agreement or service or the fact that such person is,
was or has agreed to serve as a director, officer, employee or agent of another
corporation or organization at the written request of the Company.

ITEM 7.     EXEMPTION FROM REGISTRATION CLAIMED.

            Not applicable.

ITEM 8.     EXHIBITS.

            4.1   Dianon Systems, Inc. 1999 Stock Incentive Plan, incorporated
                  by reference to Exhibit 99.B to the Company's Proxy Statement
                  on Schedule 14A, dated October 21, 1999.

            4.2   Certificate of Incorporation of the Company, incorporated by
                  reference to the Company's Registration Statement on Form S-1,
                  dated June 14, 1991 (Registration No. 33-41226).

            4.3   Bylaws of Company, incorporated by reference to the Exhibit
                  3.3. to the Company's Quarterly Report on Form 10-Q, dated
                  November 14, 1997.

            5.1   Opinion of Cadwalader, Wickersham & Taft, counsel for Company,
                  as to the legality of the securities being registered.

            23.1  Consent of Cadwalader, Wickersham & Taft (included in Exhibit
                  5.1 hereof).

            23.2  Consent of Arthur Anderson LLP.

ITEM 9.     UNDERTAKINGS.

      A. Rule 415 offering. The Company hereby undertakes:

            (1) To file, during any period in which offers or sales are being
made, a post-effective amendment to this registration statement:

                  (i) To include any prospectus required by Section 10(a)(3) of
the Securities Act;

                  (ii) To reflect in the prospectus any facts or events arising
after the effective date of the registration statement (or the most recent
post-effective amendment thereof) which, individually or in the aggregate,
represent a fundamental change in the information set forth in the registration
statement; and

                  (iii) To include any material information with respect to the
plan of distribution not previously disclosed in the registration statement or
any material change to such information in the registration statement;

                  Provided, however, that the undertakings in paragraphs
(a)(1)(i) and (a)(1)(ii) do not apply if the information required to be included
in a post-effective amendment by those paragraphs is contained in periodic
reports filed by the Company pursuant to Section 13 or 15(d) of the Exchange Act
that are incorporated by reference in the registration statement.

            (2) That, for the purpose of determining liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

            (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

      B. Filings incorporating subsequent Exchange Act documents by reference.
The Company hereby undertakes that, for purposes of determining any liability
under the Securities Act, each filing of the Company's annual report pursuant to
Section 13(a) or 15(d) of the Exchange Act (and, where applicable, each filing
of an employee benefit plan's annual report pursuant to Section 15(d) of the
Exchange Act) that is incorporated by reference in the registration statement
shall be deemed to be a new registration statement relating to the securities
offered therein and the offering of such securities at that time shall be deemed
to be the initial bona fide offering thereof.

      C. Incorporated annual and quarterly reports. The Company hereby
undertakes to deliver or cause to be delivered with the prospectus, to each
person to whom the prospectus is sent or given, the latest annual report to
security holders that is incorporated by reference in the prospectus and
furnished pursuant to and meeting the requirements of Rule 14a-3 or Rule 14c-3
under the Securities Exchange Act of 1934; and, where interim financial
information required to be presented by Article 3 of Regulation S-X is not set
forth in the prospectus, to deliver, or cause to be delivered to each person to
whom the prospectus is sent or given, the latest quarterly report that is
specifically incorporated by reference in the prospectus to provide such interim
financial information.

      D. Filing of registration on Form S-8. Insofar as indemnification for
liabilities arising under the Securities Act may be permitted to directors,
officers and controlling persons of the Company pursuant to the foregoing
provisions, or otherwise, the Company has been advised that in the opinion of
the Commission such indemnification is against public policy as expressed in the
Securities Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the Company
for expenses incurred or paid by a director, officer or controlling person of
the Company in the successful defense of any action, suit or proceeding) is
asserted by such director, officer or controlling person in connection with the
securities being registered, the Company will, unless in the opinion of its
counsel the matter has been settled by controlling precedent, submit to a court
of appropriate jurisdiction the question whether such indemnification by it is
against public policy as expressed in the Securities Act and will be governed by
the final adjudication of such issue.
SIGNATURES

            Pursuant to the requirements of the Securities Act, the Company
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the State of Connecticut on March 31, 2000.

                                       DIANON SYSTEMS, INC.
                                          (Registrant)

                                       By:  /S/ Kevin C. Johnson
                                           -------------------------------------
                                           Kevin C. Johnson
                                           President and Chief Executive Officer

            Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

          SIGNATURE                         TITLE                     DATE
          ---------                         -----                     ----

/s/ Kevin C. Johnson          President, Chief Executive        March 31, 2000
---------------------------   Officer and Director
Kevin C. Johnson

/s/ David R. Schreiber        Chief Financial Officer and       March 31, 2000
---------------------------   Director (Chief Financial
David R.  Schreiber           Officer and Corporate
                              Secretary)

/s/ John P. Davis             Director                          March 31, 2000
---------------------------
John P. Davis

/s/ Bruce K. Crowther         Director                          March 31, 2000
---------------------------
Bruce K. Crowther

/s/ Timothy Geary             Director                          March 31, 2000
---------------------------
E. Timothy Geary

/s/ G.S. Beckwith Gilbert     Director                          March 31, 2000
---------------------------
G.S. Beckwith Gilbert

                              Director                          March 31, 2000
---------------------------
Jeffrey L. Sklar