The Ludwig-McGill Cohort Study of HPV infection and cervical neoplasia is among the first to measure the incidence and clearance of HPV infections over time and to show the role of persistent HPV infection with oncogenic viral genotypes in cervical carcinogenesis. Women attending a comprehensive maternal and child health program for low-income families at a public hospital in São Paulo, Brazil were recruited (1993-1997) and followed up until 2005.