A retrospective study was done on 575 patients with atypical Papanicolaou smears obtained during a ten-year period (1974-83) at Bellevue Hospital-New York University Medical Center. The smears were classified into three categories. The first consisted of 463 patients (81%) with inflammatory atypia specifically treated for Trichomonas, Monilia, Chlamydia, Gardnerella and atrophic vaginitis. Of them, 162 patients (35% of the group) had persistent inflammatory atypia 90 days after the beginning of therapy and were subjected to colposcopic examination. The second group consisted of 86 patients (15%) with squamous atypia. That group underwent colposcopic examination. The third group, 26 patients (4%), had endocervical atypia and underwent colposcopy and endocervical curettage. Overall, of 162 patients with persistent inflammatory atypia, 36 (22%) were found to have cervical intraepithelial neoplasia (CIN); of 86 with squamous atypia, 60 (70%) had CIN; and of 26 with endocervical atypia, 15 (58%) had CIN. Fifty-eight (28%) of all the patients with CIN had lesions of severity greater than CIN 1. It appears that all patients with persistent inflammation or squamous or endocervical atypia would benefit from colposcopic screening.