Fifty-eight patients with chronic hepatitis C were followed for more than 7 years. Of them, 10 patients were found to develop hepatocellular carcinoma, 14 to develop liver cirrhosis, 30 to sustain chronic hepatitis, and 4 to show subsidence of hepatitis. Antibody to hepatitis C virus (anti-HCV) disappeared from the 4 patients whose hepatitis subsided, but it persisted in the remaining 54 patients. The mean titer of anti-HCV was almost the same at the stages of chronic hepatitis and of cancer in the 10 patients who developed hepatocellular carcinoma. These results indicate that chronic infection of hepatitis C virus may lead to hepatocellular carcinoma.