To determine the seroprevalence of human immunodeficiency virus infection in prenatal patients at high risk for HIV infection we tested 513 women from December 1985 through July 1987 at an inner-city hospital in Atlanta, Georgia. Demographic and HIV risk information was collected from all seropositive women. Twenty-nine (6%) of the 513 women tested were positive for HIV on enzyme-linked immunosorbent assay and Western blot analysis. Twenty-six (90%) of seropositive women gave a history of intravenous drug use. Two (7%) had sexual partners known to have AIDS or AIDS-related complex (ARC), and one (3%) was Haitian. Seropositive women were at remarkable risk for other sexually transmitted diseases. The majority of pregnancies ended in term births. This serosurvey defines an obstetric population with a high seroprevalence, and has stimulated us to institute routine voluntary antepartum screening for HIV.