The aim of this study was to evaluate the prevalence of hepatitis C virus infection (HCV) in Greece, to estimate its frequency in chronic liver disease and to explore the role of HCV infection in the aetiology of hepatocellular carcinoma. A series of 1034 patients with chronic liver disease of various aetioloigies and 299 patients with hepatocellular carcinoma allocated to two case-control studies was tested for anti-HCV. Twelve recent reports on HCV infection in Greece were reviewed and analyzed. The results of the present study indicate the existence of a large pool of HCV infection in Greece and an impressive spread of the virus in high-risk groups. Chronic HCV infection was found to account for 83.6% of patients with chronic non-A, non-B hepatitis parenterally transmitted, 56.5% of cases of sporadic community-acquired disease and for almost 1/4 of all patients with chronic liver disease. The relative risks for development of hepatocellular carcinoma of patients with chronic HCV infection was 6.3 in the first and 13.7 in the second case-control study, increasing to 20.0 and 18.7, respectively, when hepatitis B surface antigen (HBsAg) was positive. Serum HBV-DNA was positive and/or anti-HBc IgM levels were high in 12 of 15 (80%) patients with hepatocellular carcinoma positive only for HBsAg, and in 7 of 15 (47%) positive both for HBsAg and antibodies to HCV. The present data support the view that hepatitis B and C virus have an interacting role in the origin of hepatocellular carcinoma.