The authors derived prevalence and incidence figures for cervical human papillomavirus (HPV) infections in an unselected Finnish population of women aged 22. This paper is an epidemiologic study utilizing the mass-screening program that has been conducted in Finland for cervical cancer since the early 1960s. The authors estimated the lifetime risk of cervical HPV infections based on the figures in this program and on those derived from a random sample of 2,084 (out of 28,861) routine Papanicolaou (Pap) smears examined in their laboratory. The mass-screening program was performed between 1985-1986 focusing on a total cohort of 22-year-old women (born in 1963) in Kuopio province. In 1985, 2,013 women were invited of which 1,289 attended. One year later, 1,768 women of those 2,013 were reinvited, and the number of women screened at the second round was 1,069. The routine cervicovaginal Pap smears were taken, including a cell sample from the vagina, exocervix, and endocervix. All smears were screened for the HPV-induced cytopathic changes by the same cytopathologist. The prevalence of HPV infection among the 22-year-old women was about 3% at the beginning of the follow-up and about 7% one year later. The crude annual incidence was 7.0%. According to the estimates for the life-time risk, half of the sexually active women would experience at least one HPV infection within 10 years. Up to 79% of the Finnish females would contract at least one HPV infection between ages 20 and 79 years. This indicates that factors, which are poorly understood at the moment, exist that regulate the development of an invasive carcinoma from a CIS lesion.