Characteristics of high-risk groups for hepatocellular carcinoma (HCC) in Japan were studied to establish screening strategies for early detection of the tumor. Some 93% of patients with HCC were associated with chronic liver disease. On the other hand, 67% of patients with liver cirrhosis had HCC at autopsy. Most were related to current hepatitis virus infection. An analysis of risk factors among 120 patients with chronic hepatitis revealed that age and histological findings were independent risk factors, while HBsAg, anti-HCV, sex, history of heavy drinking, history of blood transfusion were not independent risk factors. Multivariate analysis of 239 patients with liver cirrhosis demonstrated that age, positivity for HBsAg and/or anti-HCV, family history of liver disease, hepatic reserve, and a history of radical resection were independent factors related to the development of HCC. A screening schedule for cirrhotic patients was established in accordance with these results; ultrasonography was done every three months, and tumor markers measured every two months. The screening strategy proved to be effective for the early detection of HCC and improvement of the prognosis.