The prevalence of anti-HCV was studied in a South African area endemic for hepatitis B virus. A total of 35,685 volunteer blood donors (22,034 whites, 9,218 Asians, 3,077 Africans, 1,356 coloureds), 71 haemophiliacs, 84 chronic dialysis patients, 100 antenatal attenders, 212 nurses, and 20 HIV-positive male homosexuals were tested for anti-HCV. Repeat positive second generation Ortho HCV EIA was used to determine HCV status for the blood donors; Abbott-II HCV EIA combined with a neutralisation test was used for the other risk groups. Antibody to hepatitis B core antigen (anti-HBc) was also tested in the haemophiliacs, nurses, and chronic dialysis patients. Seroprevalence for the blood donor population was 0.16, 0.34, 0.75, and 0.22% for whites, Asians, Africans, and coloureds, respectively. Of the risk groups tested, 39.4% of haemophiliacs and 4.8% of chronic dialysis patients were positive; of the remainder tested none was positive. Fifty percent of nurses, 47.9% of haemophiliacs, and 22.6% of dialysis patients had serological evidence of past exposure to hepatitis B virus (anti-HBc positive). These findings indicate a low prevalence of anti-HCV in the blood donor population, thus probably resulting in a low prevalence in groups exposed to blood and blood derivatives. The overall difference in prevalence between the race groups was significant (P < 0.0001). The high prevalence of hepatitis B virus compared to the low prevalence of HCV suggests that the main modes of transmission of the two viruses are probably different.