Genetic polymorphisms of the carcinogen-metabolizing enzymes cytochrome P450 (CYP), glutathione S-transferase (GST) M1 and N-acetyltransferase (NAT2) as well as p53 polymorphisms have been studied experimentally as susceptibility markers for hepatocellular carcinoma development in hepatocellular carcinoma cell lines and in mouse hepatocellular carcinomas. In addition, these susceptibility markers have been studied in hepatocellular carcinoma patients, in the context of coexisting alcohol consumption, smoking and/or HBV infection. To date, there is no clear evidence that susceptibility markers have an overall impact on hepatocarcinogenesis, but in subgroups of individuals, such as smokers, susceptibility markers are emerging indicators for hepatocellular carcinoma risk definition.