Toxoplasma seroprevalence was determined in 307 consecutive HIV-infected medical inpatients at the Helen Joseph Hospital, Johannesburg, South Africa, using an enzyme linked immunosorbent assay to detect immunoglobulin G (IgG) and IgM antibodies. The mean age of patients was 36 years, with a female to male ratio of 1.3 to 1. The mean CD4 count was 109 cells/mL. Toxoplasma antibodies were detected in 25 patients (8%). Twenty-two of these patients were IgG positive and IgM negative, i.e. reactivation toxoplasmosis. Only two patients (0.65%) had clinical manifestations of toxoplasmosis (one toxoplasma encephalitis and one retinitis). The risk for toxoplasma encephalitis (TE) was 0.33%. These results indicate that the toxoplasma seroprevalence and the TE risk in this population is low. The implication from this study is that in HIV-infected populations where the toxoplasma seroprevalence is low, the TE risk will be low and empiric treatment of focal brain lesions with anti-toxoplasma therapy may be inappropriate.