SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 ---------------- FORM 8-A/A Amendment No. 2 FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES PURSUANT TO SECTION 12(b) OR (g) OF THE SECURITIES EXCHANGE ACT OF 1934 DIANON Systems, Inc. ------------------------------------------------------------------------------ (Exact name of registrant as specified in its charter) Delaware 06-1128081 - -------------------------------------------------------------------------------- (State of incorporation organization) (IRS Employer Identification No.) 200 Watson Boulevard, Stratford, Connecticut 06615 - -------------------------------------------- ------------------------- (Address of principal executive offices) (Zip Code) If this form relates to the registration If this form relates to the of a class of securities pursuant to registration of a class of Section 12(b) of the Exchange Act and is securities pursuant to Section effective pursuant to General 12(g) of the Exchange Act and Instruction A.(c), please check the is effective pursuant to following box. General Instruction A.(d), please check the following box. /X/ Title of each class Name of each exchange on which to be so registered each class is to be registered - ------------------------------- -------------------------------------- Preferred Stock Purchase Rights National Association of Securities Dealers National Market System This Amendment No. 2 on Form 8A/A amends the Form 8-A filed by Dianon Systems, Inc., a Delaware corporation ("Dianon"), on May 9, 1994 with respect to Dianon's Preferred Stock Purchase Rights. Item 1. Description of Registrant's Securities to be Registered. ------------------------------------------------------- In connection with the Agreement and Plan of Merger (the "Merger Agreement"), dated as of November 10, 2002, between Laboratory Corporation of America Holdings ("LabCorp"), DaVinci Development, Inc. and Dianon Systems, Inc., Dianon and American Stock Transfer and Trust Company (the "Rights Agent"), entered into Amendment No. 2 to Rights Agreement, dated as of November 10, 2002 (the "Amendment No. 2 to Rights Agreement"), amending the Rights Agreement dated as of April 29, 1994, as amended as of October 4, 1995 ("Rights Agreement"), in order to provide that neither LabCorp nor any of its Affiliates and Associates (as defined in the Rights Agreement) shall be deemed to be an Acquiring Person (as defined in the Rights Agreement), no Distribution Date (as defined in the Rights Agreement) will have occurred, will occur or will be deemed to occur as a result of the execution and delivery of the Merger Agreement or the announcement thereof or as a result of or arising out of the consummation of the Merger as contemplated by the Merger Agreement. The foregoing description of the Amendment No. 2 to Rights Agreement is qualified in its entirety by reference to the Amendment No. 2 to Rights Agreement, a copy of which is filed herewith as Exhibit 1 and such Exhibit is incorporated herein by reference. Item 2. Exhibits. -------- 1 Amendment No. 2 to Rights Agreement, dated as of November 10, 2002, between Dianon Systems, Inc. and American Stock Transfer and Trust Company, as Rights Agent. SIGNATURE Pursuant to the requirements of Section 12 of the Securities Exchange Act of 1934, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized. DIANON Systems, Inc. Date: November 12, 2002 /s/ David R. Schreiber -------------------------------------- Name: David R. Schreiber Title: Senior Vice President, Finance and Chief Financial Officer (Principal Financial Officer and Principal Accounting Officer) INDEX OF EXHIBITS Exhibit No. Description 1 Amendment No. 2 to Rights Agreement, dated as of November 10, 2002, between Dianon Systems, Inc. and American Stock Transfer and Trust Company, as Rights Agent.