During an eight-year period, serial plasma determinations were made on members of a Gardner's syndrome family in order to see if 1. levels rise when polyps first appear, and when cancer occurs; and 2. levels fall after colectomy with ileoproctostomy, ileostomy, or rectal mucosal replacement surgery. CEA analyses were carried out in the laboratory of Norman Zamcheck, M.D., using the Roche method. Small increases in CEA titer accompanied the appearance of polyps and small decreases accompanied their removal. Further serial studies are needed to determine whether changes in CEA titer can be indicators of polyp and/or cancer occurrence.