EXHIBIT 21 SUBSIDIARIES OF THE REGISTRANT American Medical Security Holdings, Inc., a Wisconsin corporation American Medical Security, Inc., a Delaware corporation American Medical Security Insurance Company of Georgia, a Georgia corporation U & C Real Estate Partnership, a Wisconsin general partnership United Wisconsin Life Insurance Company, a Wisconsin insurance corporation Continental Plan Services, Inc., a Wisconsin corporation Nurse Healthline, Inc., a Wisconsin corporation Accountable Health Plans of America, Inc., a Texas corporation AMS HMO Holdings, Inc., a Delaware corporation American Medical Security Health Plan, Inc., a Florida corporation d/b/a American Medical Healthcare