The Program of the Fundação "Centro de Pesquisa de Oncologia" (FCPO) and the Instituto Brasileiro de Controle do Câncer (IBCC) in São Paulo has examined 980,977 women from 1970 to September 1985. Dysplasias, in situ, and invasive carcinomas were detected in 15,123 women (1.5%). The rates of false-negative and false-positive cytologic diagnoses of the program are 2.3% and 27%, respectively. The following epidemiological variables were evaluated: age, parity, age at first sexual intercourse, age at first pregnancy, education, and age at menarche. It was found that women at higher risk for cervical carcinoma in this population were those 26 years of age or older, with 4 or more pregnancies, women who had the first coitus before 18 years of age, and the first complete pregnancy before 19, as well as illiterate women or those who did not complete the first 4 years of primary school. In Brazil, the frequencies of cervical carcinomas are 25.8% for in situ and 72.2% for invasive (0.4 to 1). In this program, the corresponding percentages are 61.0% for in situ and 39.0% for invasive carcinomas (1.6 to 1). Including dysplasias, the percentages for Brazil are 56.3% for severe dysplasias plus in situ carcinomas and 43.7% for invasive carcinomas (1.3 to 1). In the FCPO/IBCC Program these percentages are 83.2% and 16.8% (5 to 1).