The number of women in state and federal prisons more than tripled between 1980 and 1990. Among incarcerated populations, women have higher rates of human immunodeficiency virus (HIV) infection than men. HIV seroprevalence ranges from 2.1% to 16.1% for men and 2.5% to 25.8% for women in U.S. prisons. The objective of this study was to determine the prevalence of cervical dysplasia among HIV-seropositive and HIV-seronegative women in a prison population and to correlate Papanicolau (Pap) smear results with demographic and clinical variables in this population at high risk for HIV infection. A review of Pap smear slides from 51 HIV-seropositive and 140 HIV-seronegative inmates was done by pathologists blinded to the women's serostatus. Cytologie findings were correlated with several variables, and differences between HIV-seropositive and HIV-seronegative women were analyzed. Thirteen of 51 (25%) HIV-seropositive women had squamous intraepithelial lesions as compared with 22 of 140 (16%) HIV-seronegative women (OR = 1.8; 95% CI 0.8-^.0). Cervical dysplasia was more prevalent in HIV-positive women with CD4 cell count <200/mm3 (OR = 2.0; 95% CI 0.4-10). Overall, changes suggestive of human papillomavirus (HPV) on Pap smear were twice as likely in the slides of HIV-seropositive women (OR = 2.5; 95% CI 1.0-6.3). Trichomoniasis was very prevalent among both seropositive (45%) and seronegative (43%) inmates. Squamous intraepithelial lesions and changes suggestive of HPV infection on Pap smears were more prevalent in HIV-seropositive than HIV-seronegative women in a prison population in which 12% of women are HIV infected and over 70% have a history of injection drug use. Trichomoniasis was very prevalent among both groups. Incarcerated women require intensive gynecologic monitoring and care.