Hepatocellular carcinoma (HCC) is common in Taiwan. The age-adjusted incidence rates have been increasing, from approxiimately 15/100 000 in the 1980s to approximately 30/100 000 recently. The main causes are chronic hepatitis B and C infections, with >90% of patients positive for hepatitis B surface antigen (HBsAg) or antibody to hepatitis C virus (anti-HCV). Before 1990, approximately 80% of patients with HCC were positive for HBsAg. The infection is mainly from perinatal mother-to-infant transmission. HCV is the second important cause, accounting for approximately 70% of HBsAg negative patients. Overall, 5-10% patients have infections of both viruses. In HBsAg negative-anti-HCV negative patients, polymerase chain reaction assay still reveals the key role of HBV. Epidemiologic studies also reveal the important role of HBV. In a nested case-control study, cumulative incidence of HCC was 10% after nine years of follow-up in hepatitis B e-antigen (HBeAg) positive carriers, with a relative risk of 60.2 compared to 9.6 in HBeAg negative carriers. The role of high viral load was confirmed when another community-based prospective study of 3644 HBsAg carriers stratified by serum hepatitis B virus (HBV) DNA levels correlated well with the occurrence of HCC, especially in carriers with levels >10(5) copies/mL. Genotype C infection contributed more to hepatocarcinogenesis than genotype B. Although HBV is dominant in causing HCC, in the last two decades the relative importance of HCV has changed. The proportion of anti-HCV positive cases has increased. In some areas of southern Taiwan where HCV infection is rampant, HCV-associated HCC have surpassed HBV-associated cases. To control hepatitis B, a mass neonatal vaccination program against hepatitis B was launched in 1984. The HBsAg carrier rate decreased from the historical 15-20% to < 1% after vaccination. Most importantly, annual incidence of childhood HCC has decreased from 0.67 to 0.19/100 000 children. To control hepatitis C, besides interrupting the transmission routes and screening blood donors with anti-HCV, treatment with interferon and ribavirin was implemented on a national basis in 2003. Through these efforts, virally-induced HCC will be controlled in 20-30 years, and a decrease of approximately 85% is anticipated by 2040. Then, HCC will not be commonly seen in Taiwanese people, and the major cause of HCC will be non-viral factors that lead to cirrhosis, such as non-alcoholic steatohepatitis.