The Authors report the results of a study on the diffusion of CIN and of invasive carcinoma of the portio in the Trieste population over the 1977-1986 decade. In order to achieve this aim all the bioptical specimens analyzed in the Institute of Pathological Anatomy and Histology of Trieste University were reviewed. Over this period 313 cases of CIN 1-2, 314 cases of CIN 3 and 289 of invasive carcinoma were diagnosed. The average age for CIN 1-2 lesions was 33.5 (range 17-78), for CIN 3 39.9 (range 18-81) and for invasive carcinoma 58.6 (range 26-89). The distribution by age group was markedly different in the three types of lesion dealt with, showing a substantial presence of preinvasive lesions under the age of 50. During the period considered a significant decrease in the incidence of invasive carcinoma was not recorded, in contrast with other reports. This datum may be explained by the fact that the number of women undergoing cyto-oncological screening has not increased over the last decade.