A study of seroprevalence of the human immunodeficiency virus involving 2384 (96%) of Mama Yemo Hospital's (Kinshasa, Zaire) 2492 personnel found 152 (6.4%) to be seropositive. Prevalence was higher among women than among men (8.1% vs 5.2%); in women peak seroprevalence (13.9%) occurred in 20-to 29-year-olds. Workers most likely to be seropositive were those who were relatively young, those who were unmarried, those reporting a blood transfusion or hospitalization during the previous ten years, and those receiving medical injections during the previous three years. Medical, administrative, and manual workers had similar seroprevalence (6.5%, 6.4%, and 6.0%, respectively), and seropositivity was not associated with any measure of patient, blood, or needle contact. These findings are consistent with other hospital-based studies indicating low risks for occupational transmission of human immunodeficiency virus.