The American Cancer Society recently has suggested changes in the frequency of Papanicolaou smear screening which, if followed, would alter current practice considerably. This study assessed the impact of the Papanicolaou smear screening interval on the prevention of advanced disease. Between July 1, 1980 and June 30, 1984, 264 women were evaluated and treated for primary epithelial carcinoma of the cervix (64% had stage I disease). Ninety-seven women (37%) had had a normal Papanicolaou smear within three years of diagnosis, including 48 women (18%) whose last normal Papanicolaou smear was within a year of diagnosis. The cytologic history was unavailable for 81 women (31%). Patients with a screening interval of greater than six years were more likely to be older, of lower socioeconomic status, and black, as compared with patients in the more frequently screened groups. Patients with a screening interval of 36 months or less were similar to those with a 37- to 72-month interval with respect to age, racial characteristics, and socioeconomic status. In this similar group of patients, a screening interval of 37-72 months was associated with a significantly larger proportion of advanced stage disease than found in more frequently screened patients. A policy of screening more frequently than every three years may therefore lead to increased survival among women who develop cervical cancer despite cytologic screening.