Summary. To investigate the contribution of hepatitis C virus (HCV) to chronic liver disease and hepatocellular carcinoma (HCC) in Korea, antibodies to HCV (anti-HCV) were tested by enzyme immunoassay in 1759 patients with chronic liver disease and HCC, and in 808 healthy adults. The prevalence of anti-HCV was 1.6% in 808 controls. Anti-HCV was present in 32 (7.7%) of 418 hepatitis B surface antigen (HBsAg)-positive and 128 (53.1%) of 241 HBsAg-negative patients with chronic hepatitis, 16 (6.0%) of 265 HBsAg-positive and 90 (30.5%) of 295 HBsAg-negative patients with liver cirrhosis, and 16 (4.8%) of 330 HBsAg-positive and 61 (29.0%) of 210 HBsAg-negative patients with HCC. Antibodies to hepatitis B core antigen (anti-HBc) were present in 80–88% of patients who were seropositive for anti-HCV and seronegative for HBsAg. Among the sera from 114 patients with HBsAg-negative and anti-HCV-positive chronic liver diseases, HBV DNA and HCV RNA were detected by polymerase chain reaction (PCR) in 54 (47.4%) and 61 (53.3%), respectively. Both HBV DNA and HCV RNA were detected in 4 (4.4%) samples. The mean age of the patients with both HBsAg and anti-HCV was not different from that of patients who were seropositive for HBsAg alone. These findings indicate that current and/or past HBV infection is still the main cause of chronic liver disease in Korea. Although multivariate analysis showed that anti-HCV is a risk factor for chronic hepatitis, cirrhosis of the liver and HCC, PCR data for HBV DNA and HCV RNA indicate that HCV infection plays only a minor role in HBsAg-positive as well as in HBsAg-negative liver disease and does not accelerate the development of HCC in HBV carriers.