Sera from 102 black patients with primary hepatocellular carcinoma (PHC) and hepatitis B surface antigenemia were tested for immunoglobulin M antibody against hepatitis B core (IgM anti-HBc), hepatitis B e antigen (HBeAg), and hepatitis B viral (HBV) DNA. Their prevalences were compared to those of a control group of 124 age and sex matched black HBV carriers without tumor. IgM anti-HBc was present in 68.6%, HBeAg in 32.3%, and HBV-DNA in 26.7% of the patients. In the control population, IgM anti-HBc was present in 45%, HBeAg was detected in 3.2%, and HBV-DNA in 25.8%. We conclude that IgM anti-HBc is present appreciably more often than either HBeAg or HBV-DNA in patients with PHC. HBeAg or IgM anti-HBc in serum of HBsAg positive carriers may predict an added risk of PHC development in South African blacks.