During the years 1961-1986 a total of 378 CIN lesions were diagnosed among 4875 women screened for cervical pathology; 285 of them were followed-up for a minimum of 5 years. All 169 cases diagnosed as CIN-3 and 18 classified as CIN-2 were treated surgically, whereas 89 patients diagnosed as CIN-1 and 65 classified as CIN-2 were treated conservatively. Finally, 37 cases (23 diagnosed as CIN-1 and 14 diagnosed as CIN-2) did not receive any treatment. Of the 187 women treated surgically, 6 (3.8%) showed, within the five year follow-up period, progression or recurrence of the disease, which necessitated either additional surgery or radiation; 5 of these cases had been classified as severe dysplasia (CIN-3). Recurrence or progression necessitating major surgery, occurred in 8 (5.1%) of the 154 patients treated conservatively; 5 of these cases were classified as moderate dysplasia (CIN-2). The data indicate that present diagnostic procedures allow a better selection of patients to be submitted to surgery, increasing the proportion of those treated conservatively, without jeopardizing their prognosis.