To characterize the epidemiologic characteristics of human immunodeficiency virus type 1 infection in an urban prenatal population in the southeastern United States, we conducted serial routine voluntary antenatal human immunodeficiency virus antibody testing and obtained self-reported human immunodeficiency virus risk behavior profiles on women registering for prenatal care. From July 1987 to June 1990, 23,432 women registered for prenatal care. The majority of women (95%) consented to human immunodeficiency virus antibody testing and completed risk behavior profiles. The cumulative incidence of human immunodeficiency virus infection increased from 3.5 per 1000 in 1987 and 1988 to 5.3 per 1000 in 1989 and 1990. A history of "crack" cocaine use emerged as a significant risk factor for infection (p less than 0.01). The majority (70%) of human immunodeficiency virus-infected women did not self-acknowledge risk factors for infection and would not have been identified if screening had been targeted. The increasing incidence of human immunodeficiency virus type 1 infection in our prenatal population reinforces the need for our continued routine voluntary antenatal human immunodeficiency virus screening and risk behavior assessment.