<Page>

                                                                    EXHIBIT 3.31

                                                       STATE OF DELAWARE
                                                      SECRETARY OF STATE
                                                   DIVISION OF CORPORATIONS
                                                   FILED 09:00 AM 03/09/1998
                                                      981089537 - 2868762

                          CERTIFICATE OF INCORPORATION

                                       OF

                             AMERIPATH NY LABS INC.

                                    ARTICLE I.

                                      NAME

     The name of the corporation is AMERIPATH NY LABS, INC. (hereinafter called
the "Corporation").

                                   ARTICLE II.

                           REGISTERED AGENT AND OFFICE

     The address of the Corporation's registered office in the State of Delaware
is 1013 Centre Road, City of Wilmington 19805, County of New Castle and the name
of its registered agent at such address is Corporation Service Company.

                                  ARTICLE III.

                                     PURPOSE

     The purpose for which the Corporation is formed is to engage in any lawful
act or activity for which corporations may be organized under the General
Corporation Law of Delaware.

                                   ARTICLE IV.

                                  CAPITAL STOCK

     The aggregate number of shares of capital stock which the Corporation shall
have the authority to issue is 100 shares of Common Stock, par value $0.01 per
share.

     All shares of Common Stock shall be identical and shall entitle the holders
thereof to the same rights and privileges:

     A.     VOTING RIGHTS. Except as otherwise required by law, all rights to
            vote and all voting power shall be vested exclusively in the holders
            of the Common Stock.

                                       -1-
<Page>

     B.     DIVIDENDS. The holders of the Common Stock shall to entitled to
            receive when, as and if declared by the Board of Directors, out of
            funds legally available therefor, dividends payable in cash, stock
            or otherwise.

     C.     LIQUIDATING DISTRIBUTIONS. Upon any liquidation, dissolution or
            winding-up of the Corporation, whether voluntary or involuntary, the
            remaining net assets of the Corporation shall be distributed pro
            rata to the holders of the Common Stock in accordance with their
            respective rights and interests.

                                   ARTICLE V.

                                    DIRECTORS

     The Corporation's Board of Directors shall consist of not fewer than one
(1) nor more then five (5) directors, and shall initially consist of two (2)
directors. The number of directors within these limits may be increased or
decreased from time to time as provided in the Bylaws of the Corporation. The
names of the initial Directors of the Corporation are as follows:

                                 Robert P. Wynn
                                  James C. New

                                   ARTICLE VI.

                                     BYLAWS

     In furtherance and not in limitation of the powers conferred by the laws of
the State of Delaware:

     A.     The Board of Directors of the Corporation is expressly authorized
            to adopt, amend or repeal the Bylaws of the Corporation.

     B.     Elections of Directors need not be by written ballot unless the
            Bylaws of the Corporation shall so provide.

     C.     The books of the Corporation may be kept at such place within or
            without the State of Delaware as the Bylaws of the Corporation may
            provide or as may be designated from time to time by the Board of
            Directors of the Corporation.

     D.     Any action required or permitted to be taken at any meeting of
            the Board of Directors, may be taken without meeting only if all of
            the Directors consent thereto in writing.

                                       -2-
<Page>

                                  ARTICLE VII.

                             LIMITATION OF LIABILITY

     No director shall be personally liable to the Corporation or the holders of
shares of capital stock for monetary damages for breach of fiduciary duty as a
director, except (i) for any breach of the duty of loyalty of such director to
the Corporation or such holders, (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 General Corporation Law of Delaware, or (iv) for any
transaction from which such director derives an improper personal benefit. No
amendment to or repeal of this provision shall apply to or have any effect on
the liability of alleged liability of any Director for or with respect to any
acts or omissions of such Director occurring prior to such amendment or repeal.
If the Law .of the Corporation's state of incorporation is hereafter amended to
authorize corporate action further eliminating or limiting the personal
liability of directors, then the liability of a Director of this Corporation
shall be eliminated or limited to the fullest extent then permitted. No repeal
or modification of this Article VII shall adversely affect any right of or
protection afforded to a Director of the Corporation existing immediately prior
to such repeal or modification.

                                  ARTICLE VIII.

                                 INDEMNIFICATION

     This Corporation shall indemnify and may advance expenses to its Officers
and Director to the fullest extent permitted by law in existence either now or
hereafter in effect. Without limiting the generality of the foregoing, the
Bylaws may provide for indemnification and advancement of expenses to the
Corporation's Officers, Directors, employees and agents on such terms and
conditions as the Board of Directors may from time to time deem appropriate or
advisable.

                                   ARTICLE IX.

                                  INCORPORATOR

     The name of the incorporator is Keith Wasserstrom and the address of the
incorporator is 515 East Las Olas Boulevard, Suite 1500, Fort Lauderdale,
Florida 33301.

                                       -3-
<Page>

                                   ARTICLE X.

                                   AMENDMENTS

     Except as provided herein, from time to time any of the provisions of this
Certificate of Incorporation may be amended, altered or repealed, and other
provisions authorized by the laws of the State of Delaware at the time in force
may be added or inserted in the manner and at the time prescribed by said laws,
and all rights at any time conferred upon the stockholders of the Corporation by
this Certificate of Incorporation are granted subject to the provisions of that
Article IX.

     IN WITNESS WHEREOF, the undersigned, being the Incorporator named above,
for the purpose of forming a corporation pursuant to the General Corporation Law
of the State of Delaware, has signed this Certificate of Incorporation this 9th
day of March, 1998.


                                                /s/ Keith Wasserstrom
                                                --------------------------------
                                                KEITH WASSERSTROM, Incorporator

                                       -4-
<Page>

                                                         STATE OF DELAWARE
                                                        SECRETARY OF STATE
                                                     DIVISION OF CORPORATIONS
                                                    FILED 09:00 AM 03/09/1998
                                                       981089537 - 2868762

                            CERTIFICATE OF AMENDMENT
                                       OF
                          CERTIFICATE OF INCORPORATION
                                       OF
                             AMERIPATH NY LABS, INC.

     AMERIPATH NY LABS, INC., a corporation organized and existing under and by
virtue of the General Corporation Law of the State of Delaware, DOES HEREBY
CERTIFY;

          FIRST:   That the Board of Directors of said corporation, by unanimous
written consent, adopted the following resolution:

     RESOLVED, that the Certificate of Incorporation of the corporation be
     amended by changing Article I so that, as amended, said Article shall be
     and read as follows:

                                   "ARTICLE I

                                      NAME

          The name of the corporation is AmeriPath New York, Inc."

          SECOND: That the said amendment has been consented to and authorized
     by the holder of all of the issued and outstanding stock entitled to vote
     by a written consent given in accordance with the provisions of Section 228
     of the General Corporation Law of the State of Delaware.

          THIRD: That the aforesaid amendment was duly adopted in accordance
     with the applicable provisions of Sections 242 and 228 of the General
     Corporation Law of the State of Delaware.

          IN WITNESS WHEREOF said corporation has caused this Certificate to be
     signed by its Secretary this 15th of March, 1999.

                                                /s/ Robert P. Wynn
                                                --------------------------------
                                                Robert P. Wynn, Secretary

<Page>

                                SECOND AMENDMENT
                                     TO THE
                          CERTIFICATE OF INCORPORATION
                                       OF
                            AMERIPATH NEW YORK, INC.

               (Under Section 242 of the General Corporation Law)

     Pursuant to the provisions of Section 242 of the General Corporation Law of
the State of Delaware (the "GCL"), AmeriPath New York, Inc. (the "Corporation")
hereby certifies as follows;

     FIRST:     The Certificate of Incorporation was filed with the Delaware
Secretary of State on March 9, 1998. On March 17, 1999 a First Amendment to the
Certificate of Incorporation of the Corporation was filed with the Delaware
Secretary of State to change the name of Ameripath NY Labs, Inc. to AmeriPath
New York, Inc. (the Certificate of Incorporation of the Corporation, as so
amended, the "Certificate").

     SECOND:    Article III of the Certificate is hereby amended to change the
purposes of the Corporation to include the power to own and operate a clinical
laboratory pursuant to the New York Public Health Law 575 and to operate an
accredited dermatopathology fellowship training program so that it shell
henceforth read in its entirety as Follows:

                                  "ARTICLE III
                                     PURPOSE

     The purposes for which the Corporation is formed is to: (i) own and operate
     one or more clinical laboratories pursuant to the New York Public Health
     Law Section 575 ET SEQ., (ii) operate an accredited dermatopathology
     fellowship training program, and (iii) further to engage in any lawful act
     or activity for which corporations may be organized under the General
     Corporation Law of Delaware, provided, however, that nothing herein shall
     authorize the Corporation to; (a) operate or maintain an institution of
     higher learning or to grant general degrees, (b) engage in the practice of
     the profession of medicine or any other profession required to be licensed
     by Title VIII of the New York Education Law except to the extent consistent
     with the operation of a clinical laboratory, and (C) provide professional
     training required for admission to the profession of medicine or any other
     profession subject to licensure under Title VIII of the New York Education
     Law."

     THIRD:     The foregoing amendment to the Certificate was duly by the Board
of Directors and the stockholders of the Corporation in accordance with the
provisions of Section 228 and Section 242 of the GCL.

<Page>

     IN WITNESS WHEREOF, the Corporation has caused this Second Amendment to the
Certificate of Incorporation to be executed this 10th day of JANUARY 2000, by an
officer thereunto duly authorized.

                                             AMERIPATH NEW YORK, INC.


                                             By:/s/ Robert P. Wynn
                                                -----------------------------
                                                Name:  Robert P. Wynn
                                                Title: Executive Vice President
                                                       and Secretary