UNITED STATES
                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                                 ____________


                                Amendment No. 1
                                      to
                                  FORM 8-A

               FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                    PURSUANT TO SECTION 12(b) OR (g) OF THE
                        SECURITIES EXCHANGE ACT OF 1934


                     AMERICAN MEDICAL SECURITY GROUP, INC.
-------------------------------------------------------------------------------
            (Exact name of registrant as specified in its charter)

                Wisconsin                            39-1431799
-----------------------------------------      ----------------------------
(State of incorporation or organization)          (I.R.S. Employer
                                                 Identification No.)

           3100 AMS Boulevard
          Green Bay, Wisconsin                          54313
-----------------------------------------      ----------------------------
(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               securities pursuant to Section
and is effective pursuant to General           12(g) of the Exchange Act and
Instruction A.(c), please check the            is effective pursuant to
following box.  [ X ]                          General Instruction A.(d),
                                               please check the following
                                               box.  [  ]

Securities Act registration statement file number to which this form relates:
 N/A (if applicable)

Securities to be registered pursuant to Section 12(b) of the Act:

     Title of each class                      Name of each exchange on which
     to be so registered                      each class is to be registered
     -------------------                      ------------------------------

Preferred Share Purchase Rights                  New York Stock Exchange
(associated with the Common Stock)

Securities to be registered pursuant to Section 12(g) of the Act:

                                     None
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                               (Title of Class)






Item 1.   Description of Registrant's Securities to be Registered.

                  On September 15, 2004, American Medical Security Group,
Inc., a Wisconsin corporation (the "Company"), entered into an Agreement and
Plan of Merger (the "Merger Agreement"), by and among the Company, PacifiCare
Health Systems, Inc., a Delaware corporation ("Parent"), and Ashland
Acquisition Corp., a Wisconsin corporation and a wholly-owned subsidiary of
Parent ("Merger Subsidiary"), pursuant to which Merger Subsidiary will merge
with and into the Company (the "Merger"), upon the terms and subject to the
conditions set forth in the Merger Agreement. In connection with the Merger
Agreement and the transactions contemplated thereby, the Board of Directors of
the Company authorized the amendment of the Rights Agreement, dated as of
August 9, 2001, as amended (the "Rights Agreement"), by and between the
Company and Firstar Bank, N.A. (with LaSalle Bank, N.A., as successor rights
agent (the "Rights Agent")). Capitalized terms used but not defined herein
shall have the meanings assigned thereto in the Rights Agreement.

                  On September 15, 2004, the Company and the Rights Agent
executed an amendment (the "Amendment") to the Rights Agreement. The Amendment
provides, among other matters, that (i) none of Parent, Merger Subsidiary or
any of their respective Affiliates or Associates shall be, become or be deemed
an Acquiring Person by virtue of the approval, execution, delivery,
announcement or performance of the Merger Agreement or the consummation of the
transactions contemplated thereby, including the Merger, and (ii) no Shares
Acquisition Date, no Triggering Event, no Distribution Date, no Section
11(a)(ii) Event and no Section 13 Event shall be deemed to have occurred by
reason of the approval, execution, delivery, announcement or performance of
the Merger Agreement or consummation of the transactions contemplated thereby,
including the Merger. The Amendment also provides that the Rights Agreement
and the Rights established thereby will terminate in all respects immediately
prior to the Effective Time (as defined in the Merger Agreement).

                  The Rights Agreement, including the form of Rights
Certificate, is filed as Exhibit 1 to the Company's Registration Statement on
Form 8-A, filed with the Securities and Exchange Commission (the "SEC") on
August 14, 2001 and is incorporated herein by reference. The Appointment and
Assumption Agreement, dated as of December 17, 2001, by and between the
Company and the Rights Agent is included as Exhibit 4.2 to the Company's
Current Report on Form 8-K, filed with the SEC on February 5, 2002 and is
incorporated herein by reference. The Amendment to Rights Agreement, dated as
of February 1, 2002, by and between the Company and the Rights Agent is
included as Exhibit 4.1 to the Company's Current Report on Form 8-K, filed
with the SEC on February 5, 2002 and is incorporated herein by reference. The
Amendment to Rights Agreement, dated as of June 4, 2002, by and between the
Company and the Rights Agent is included as Exhibit 4.4(d) to the Company's
Current Report on Form 8-K, filed with the SEC on June 19, 2002 and is
incorporated herein by reference. The Amendment is filed as Exhibit 4.5 hereto
and is incorporated herein by reference. The foregoing description of the
Rights Agreement and the Amendment does not purport to be complete and is
qualified in its entirety by reference to such exhibits.

Item 2.   Exhibits.


          4.1        Rights Agreement, dated as of August 9, 2001, by and
                     between the Company and Firstar Bank, N.A., as rights
                     agent (incorporated by reference to Exhibit 1 to the
                     Company's Registration Statement on Form 8-A, filed with
                     the SEC on August 14, 2001)

          4.2        Appointment and Assumption Agreement, dated as
                     of December 17, 2001, by and between the Company
                     and the Rights Agent (incorporated by reference
                     to Exhibit 4.2 to the Company's Current Report
                     on Form 8-K, filed with the SEC on February 5,
                     2002)

          4.3        Amendment to Rights Agreement, dated as of February 1,
                     2002, by and between the Company and the Rights Agent
                     (incorporated by reference to Exhibit 4.1 to the
                     Company's Current Report on Form 8-K, filed with the SEC
                     on February 5, 2002)

          4.4        Amendment to Rights Agreement, dated as of June 4, 2002,
                     by and between the Company and the Rights Agent
                     (incorporated by reference to Exhibit 4.4(d) to the
                     Company's Current Report on Form 8-K, filed with the SEC
                     on June 19, 2002)

          4.5        Amendment to Rights Agreement, dated as of September 15,
                     2004, by and between the Company and the 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, thereto duly authorized.

Date: September 15, 2004                  AMERICAN MEDICAL SECURITY
                                          GROUP, INC.

                                          By: /s/ Timothy J. Moore
                                              --------------------------------
                                              Name:   Timothy J. Moore
                                              Title:  Senior Vice President of
                                                      Corporate Affairs, General
                                                      Counsel and Secretary





                                 EXHIBIT INDEX

          Exhibit No.                   Description
          -----------                   -----------

          4.1           Rights Agreement, dated as of August 9, 2001, by and
                        between the Company and Firstar Bank, N.A., as rights
                        agent (incorporated by reference to Exhibit 1 to the
                        Company's Registration Statement on Form 8-A, filed
                        with the SEC on August 14, 2001)

          4.2           Appointment and Assumption Agreement, dated as of
                        December 17, 2001, by and between the Company and the
                        Rights Agent (incorporated by reference to Exhibit 4.2
                        to the Company's Current Report on Form 8-K, filed
                        with the SEC on February 5, 2002)

          4.3           Amendment to Rights Agreement, dated as of February 1,
                        2002, by and between the Company and the Rights Agent
                        (incorporated by reference to Exhibit 4.1 to the
                        Company's Current Report on Form 8-K, filed with the
                        SEC on February 5, 2002)

          4.4           Amendment to Rights Agreement, dated as of June 4,
                        2002, by and between the Company and the Rights Agent
                        (incorporated by reference to Exhibit 4.4(d) to the
                        Company's Current Report on Form 8-K, filed with the
                        SEC on June 19, 2002)

          4.5           Amendment to Rights Agreement, dated as of September
                        15, 2004, by and between the Company and the Rights
                        Agent