de Ribamar Pinho-França J, et al. - The incidence of atypical cells and their risk factors in an opportunistic screening context were investigated. Analysis of 86,609 women living in Maranhão State - Brazil, who had a negative cervical cytological test recorded in the Cervical Cancer Information System in 2007 and who had at least 1 follow-up test up to December 31, 2012, formed the bases of this cohort study. The cumulative incidence of low grade squamous intraepithelial lesion reached 10.7 per 1,000 and that of high-grade squamous intraepithelial lesions and cancer (HSIL+) was 3.9 per 1,000 at 60 months follow-up. As Municipal Human Development Index decreased, a significant tendency towards increased incidence rate and risk of presenting HSIL + was observed.