Of 177 gynecologic outpatients with cervical dysplasia studied, 29 (16%) were found to excrete Chlamydia trachomatis from their urogenital tract. Sera collected from 93 of these patients were significantly more often positive for and showed higher levels of antichlamydial micro-complement fixation (CF) and immunofluorescence (IF) antibodies than sera obtained from the controls. However, when the sera were tested for anti-herpesvirus type II (HSV-II) and cytomegalovirus (CMV) antibodies, no difference between the cases and the controls were encountered.