
<PAGE>   1
 
    AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON OCTOBER 21, 1997
 
                                                     REGISTRATION NO. 333-
================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                             ---------------------
 
                                    FORM S-1
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                             ---------------------
 
                                AMERIPATH, INC.
             (Exact name of registrant as specified in its charter)
 
<TABLE>
<S>                              <C>                              <C>
           DELAWARE                           8099                          65-0642485
(State or other jurisdiction of   (Primary Standard Industrial           (I.R.S. Employer
incorporation or organization)     Classification Code Number)          Identification No.)
</TABLE>
 
                             ---------------------
                          7289 GARDEN ROAD, SUITE 200
                          RIVIERA BEACH, FLORIDA 33404
                                 (561) 845-1850
  (Address, including zip code, and telephone number, including area code, of
                    registrant's principal executive office)
                             ---------------------
                                  JAMES C. NEW
                     PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                AMERIPATH, INC.
                          7289 GARDEN ROAD, SUITE 200
                          RIVIERA BEACH, FLORIDA 33404
                                 (561) 845-1850
 (Name, address, including zip code, and telephone number, including area code,
                             of agent for service)
                             ---------------------
                          COPIES OF COMMUNICATIONS TO:
 
<TABLE>
<C>                                          <C>
          DANIEL H. ARONSON, ESQ.                      J. VAUGHAN CURTIS, ESQ.
         GREENBERG TRAURIG HOFFMAN                        ALSTON & BIRD LLP
       LIPOFF ROSEN & QUENTEL, P.A.                      ONE ATLANTIC CENTER
   515 E. LAS OLAS BOULEVARD, SUITE 1500             1201 WEST PEACHTREE STREET
      FORT LAUDERDALE, FLORIDA 33301                      ATLANTA, GA 30309
              (954) 765-0500                               (404) 881-7000
</TABLE>
 
                             ---------------------
    APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:  As soon as
practicable after the effective date of this Registration Statement.
 
    If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, check the following box.  [ ]
 
    If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration number of the earlier effective
registration statement for the same offering.  [X] 333-34265
 
    If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [ ] ______
 
    If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box.  [ ]
                             ---------------------
                        CALCULATION OF REGISTRATION FEE
 
<TABLE>
<CAPTION>
=======================================================================================================================
                                                                                 PROPOSED MAXIMUM
   TITLE OF EACH CLASS OF SECURITIES         AMOUNT TO       PROPOSED MAXIMUM        AGGREGATE           AMOUNT OF
           TO BE REGISTERED              BE REGISTERED(1)    OFFERING PRICE(2)   OFFERING PRICE(2)  REGISTRATION FEE(3)
-----------------------------------------------------------------------------------------------------------------------
<S>                                     <C>                 <C>                 <C>                 <C>
Common Stock, $.01 par value per
  share................................       690,000             $16.00            $11,040,000           $5,087
=======================================================================================================================
</TABLE>
 
(1) Includes 750,000 shares of Common Stock which may be purchased by the
    Underwriters pursuant to an over-allotment option.
(2) Estimated solely for the purpose of calculating the registration fee.
(3) 5,750,000 shares were registered under Registration No. 333-34625 and a
    filing fee of $26,137 was previously paid with the earlier registration
    statement.
================================================================================
<PAGE>   2
 
                                EXPLANATORY NOTE
 
    THIS REGISTRATION STATEMENT RELATES TO THE PUBLIC OFFERING OF COMMON STOCK
OF AMERIPATH, INC. CONTEMPLATED BY A REGISTRATION STATEMENT ON FORM S-1,
REGISTRATION NO. 333-34265 (THE "PRIOR REGISTRATION STATEMENT"), AND IS FILED
SOLELY TO INCREASE THE NUMBER OF SHARES TO BE OFFERED IN SUCH OFFERING BY
690,000 SHARES, INCLUDING UP TO 90,000 SHARES THAT MAY BE SOLD BY SELLING
STOCKHOLDERS OR THE COMPANY PURSUANT TO THE UNDERWRITERS' OVER-ALLOTMENT OPTION.
THE CONTENTS OF THE PRIOR REGISTRATION STATEMENT ARE HEREBY INCORPORATED BY THIS
REFERENCE.
 
                                       1.1
<PAGE>   3
 
                                   SIGNATURES
 
     Pursuant to the requirements of the Securities Act of 1933, the registrant
has duly caused this registration statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in the City of Riviera Beach, State of
Florida, on October 21, 1997.
 
                                       AMERIPATH, INC.
 
                                       By:         /s/ JAMES C. NEW
                                         ---------------------------------------
                                                      James C. New
                                          President and Chief Executive Officer
 
                               POWER OF ATTORNEY
 
     KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below hereby constitutes and appoints James C. New and Robert P. Wynn his true
and lawful attorneys-in-fact, each acting alone, with full powers of
substitution and resubstitution, for him and in his name, place and stead, in
any and all capacities, to sign any or all amendments, including any
post-effective amendments, to this registration statement, and any additional
registration statements filed pursuant to Rule 462 under the Securities Act of
1933 relating hereto, and to file the same, with exhibits thereto, and other
documents in connection therewith, with the Securities and Exchange Commission,
hereby ratifying and confirming all that said attorneys-in-fact or their
substitutes, each acting alone, may lawfully do or cause to be done by virtue
hereof.
 
     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 date indicated.
 
<TABLE>
<CAPTION>
                      SIGNATURE                                     TITLE                       DATE
                      ---------                                     -----                       ----
<S>                                                    <C>                               <C>
                  /s/ JAMES C. NEW                     President, Chief Executive          October 21, 1997
-----------------------------------------------------    Officer and Director
                    James C. New                         (principal executive officer)
 
                          *                            Chief Operating Officer and         October 21, 1997
-----------------------------------------------------    Director
                  Alan Levin, M.D.
 
                 /s/ ROBERT P. WYNN                    Executive Vice President and        October 21, 1997
-----------------------------------------------------    Chief Financial Officer
                   Robert P. Wynn                        (principal financial officer
                                                         and principal accounting
                                                         officer)
 
                          *                            Chairman of the Board and           October 21, 1997
-----------------------------------------------------    Director
                  Thomas S. Roberts
 
                          *                            Director                            October 21, 1997
-----------------------------------------------------
              Timothy Kilpatrick, M.D.
 
                          *                            Director                            October 21, 1997
-----------------------------------------------------
              C. Arnold Renschler, M.D.
 
                                                       Director
-----------------------------------------------------
                  E. Roe Stamps, IV
</TABLE>
 
*By:         /s/ JAMES C. NEW
     ------------------------------------
                 James C. New
               Attorney-in-fact
<PAGE>   4
                                 EXHIBIT INDEX


<TABLE>
<CAPTION>
Exhibit
Number                                                                              Page Number
------                                                                              -----------
<S>                                                                                  <C>
5.1  Opinion of Greenberg, Traurig, Hoffman, Lipoff, Rosen & Quentel, P.A.
     as to the validity of the Common Stock being registered

23.1 Consent of Greenberg, Traurig, Hoffman, Lipoff, Rosen & Quentel, P.A.
     (included in its opinion filed as Exhibit 5.1)

23.2 Consent and Report on Schedules of Deloitte & Touche LLP 

23.3 Consent of Deloitte & Touche LLP (Fort Lauderdale, Florida) 

23.4 Consent of Deloitte & Touche LLP (Orlando, Florida) 

23.5 Consent of Deloitte & Touche LLP (Cincinnati, Ohio) 

23.6 Consent of Deloitte & Touche LLP (Dallas, Texas) 

23.7 Consent of Deloitte & Touche LLP (Indianapolis, Indiana) 

*24  Power of attorney from officers and directors of the Company
     signing by an attorney-in-fact
</TABLE>

--------------------
*  Incorporated by reference from the Registration Statement on Form S-1 of the
Registrant, Registration No. 333-34265.


