HIV-infected women have high risk for precancerous lesions of the uterine cervix. We studied the prevalence and risk factors of squamous intraepithelial lesions (SIL) among systematically followed HIV-infected women enrolled from a population with low HIV prevalence. The study population consisted of 108 HIV-infected women enrolled between 1989 and 2003 with a mean follow-up 4.4 years. Risk factors of SIL were assessed based on samples collected during 2000-02. The overall rates of atypical glandular cells of uncertain significance (AGUS), atypical squamous cells of uncertain significance (ASCUS), low-grade SIL (LSIL) and high-grade SIL (HSIL) were 4, 24, 15 and 5%, respectively. Reduced CD4-lymphocyte count was associated with an increased prevalence of SIL, whereas duration of HIV infection (< or > or =5 years), use of antiretroviral medication, or HIV viral load (<50 or > or =50 copies/mL) was not. The cumulative risk of developing SIL after 1 and 5 years was 17% (95% confidence interval [CI] 7-27%) and 48% (95% CI 33-63%), respectively. The cumulative risk of SIL was increased among women younger than 31 years (P = 0.04) as well as in women displaying high initial HIV viral load (P = 0.01). Our results from a low HIV-incidence population re-emphasize the importance of guidelines for cytologic screening of HIV-seropositive women.