We investigated a relationship between the risk factors for metabolic syndrome, such as obesity, diabetes mellitus, hypertension, and hyperlipidemia, and the pathogenesis and outcome of hepatocellular carcinoma (HCC). One hundred twenty four patients who underwent curative resections for HCC were classified into 3 groups: those patients who were positive for hepatitis B surface antigen (group B), those positive for antibody to hepatitis C virus (group C), and those negative for both of them (non-B non-C) (group NBNC). The preoperative laboratory data, risk factors for metabolic syndrome, history of alcohol abuse, and outcome after surgery were investigated. The presence of non-alcoholic steatohepatitis (NASH) was also evaluated. The incidence of diabetes mellitus, hyperlipidemia, and alcohol abuse, and the serum level of triglyceride were significantly higher in group NBNC than in groups B or C. The risk factors for metabolic syndrome tended to lower the survival rates in group B and C, but not in group NBNC. Three of the 37 non-B non-C patients were associated with NASH. It is suggested that the pathogenesis of non-B non-C HCC may be more closely associated with the risk factors for metabolic syndrome than that of hepatitis virus related HCC.