Although the iron-loading disease, hereditary hemochromatosis, has a strong causal association with hepatocellular carcinoma (HCC), the carcinogenic potential of dietary iron overload in Black Africans is not known. We investigated this potential by evaluating iron status, alcohol consumption, markers for hepatitis B (HBV) and C virus (HCV) infections, and exposure to dietary aflatoxin B1 in 24 rural patients with this tumor, 48 race-, sex-, and age-matched hospital-based controls, and 75 related or unrelated close family members of the cancer patients. Iron overload was defined as a raised serum ferritin concentration in combination with a transferrin saturation > or = 60%, and was confirmed histologically when possible. Among 24 patients and 48 hospital controls, the risk of developing HCC in the iron-loaded subjects was 10.6 (95% confidence limits of 1.5 and 76.8) relative to individuals with normal iron status, after adjusting for alcohol consumption, chronic HBV and HBC infections, and exposure to aflatoxin B1. The risk of HCC in subjects with HBV infection was 33.2 (7.2, 153.4) (odds ratio [95% confidence limits]), HCV infection 6.4 (0.3, 133.5), and alcohol consumption 2.0 (0.5, 8.2). Aflatoxin B1 exposure did not appear to increase the risk of HCC. The population attributable risk of iron overload in the development of HCC was estimated to be 29%. Among 20 cancer patients and 75 family members, the risk of developing HCC with iron overload was 4.1 (0.5, 32.2). We conclude that dietary iron overload may contribute to the development of HCC in Black Africans.