Chronic infection with hepatitis C virus (HCV) is a major risk factor for development of hepatocellular carcinoma (HCC). In general, HCC develops only after 2 or more decades of HCV infection and the increased risk is restricted largely to patients with cirrhosis or advanced fibrosis. Factors that predispose to HCC among HCV-infected persons include male sex, older age, hepatitis B virus (HBV) coinfection, heavy alcohol intake, and possibly diabetes and a transfusion-related source of HCV infection. Viral factors play a minor role. The likelihood of development of HCC among HCV-infected persons is difficult to determine because of the paucity of adequate long-term cohort studies; the best estimate is 1% to 3% after 30 years. Once cirrhosis is established, however, HCC develops at an annual rate of 1% to 4%. Successful antiviral therapy of patients with HCV-related cirrhosis may reduce the future risk for HCC. The incidence of and mortality caused by all HCC has doubled in the United States over the past 25 years, an increase that has affected all ethnic groups, both sexes, and younger age groups. Given the current prevalence of HCV infection among persons 30 to 50 years of age, the incidence and mortality rates of HCC are likely to double in the United States over the next 10 to 20 years. Future research should focus on improving understanding of the incidence and risk factors for HCC, causes of HCV-related carcinogenesis, means of early detection, and better treatment for HCC. (HEPATOLOGY 2002;36:S74–S83).