The precise nature of the relationship between cirrhosis and HCC remains to be elucidated. However, it seems likely that no single explanation will cover the various forms the association takes in different parts of the world. In the high HCC incidence regions of sub- Saharan Africa and the Far East, an etiology common to the two disorders, HBV and possibly other hepatitis viruses, seems to account for the majority of cases. The role of aflatoxin in these areas is uncertain because it appears not to cause cirrhosis in man. In populations in which HCC is uncommon, alcoholic cirrhosis is the most frequent association of HCC. There is no convincing evidence to support a shared etiology in this situation because alcohol has not thus far been proved to be directly oncogenic for the liver. Possibly, cirrhosis renders the hepatocytes more susceptible to environmental carcinogenic factors. The same explanation may apply to hemochromatosis. There is at present little evidence for the postulate that HCC is an inevitable consequence of the hyperplasia of cirrhosis.