Human immunodeficiency virus infection is the leading medical problem among prison inmates in several states. In 1988 a blinded seroprevalence study was conducted on 480 New York female prison entrants to determine the prevalence of and risk factors for HIV infection in this population. Ninety (18.8 percent) women were HIV-seropositive. Seroprevalence was highest among women ages 30-39 (25.0 percent) and varied by ethnicity (Hispanics, 29.4 percent; Blacks, 14.4 percent; Whites, 7.1 percent) and residence (New York City, 23.8 percent; Upstate, 5.1 percent). Nearly half (44.9 percent) of the 136 acknowledged intravenous drug users and one-third (33.8 percent) of the 71 women with a positive syphilis serology were HIV-seropositive. There was no difference in fertility histories between seropositive and seronegative women, and two of 21 pregnant women were seropositive. This study led to increased clinical and prevention services for this high-risk population.