The importance of hepatitis C virus (HCV) infection as a cause of chronic liver disease has become clear with the introduction of serologic detection methods. On the basis of epidemiologic evidence the parenteral way of infection has been considered to be the most important one. However, the epidemiologic data regarding the significant route of infection are still limited. To study the ways of HCV-infection and their possible influence on the course of the disease, 73 patients with chronic hepatitis C infection were examined. Setting was the out-patient department of Gastroenterology of our University Hospital. Patients history, completed by a questionnaire, laboratory findings and liver histology were analysed. The study indicated that in 50% of the patients transmission had occurred through parenteral infection, the other 50% had been infected through the non-parenteral (sporadic) way. The study revealed further that the way of infection has an influence on the progression of liver disease with the patients infected sporadically showing histologically more serious hepatic changes. In 50 patients HCV-infection was the only cause of their chronic liver disease, in 23 patients additional pathogenic factors were detected. These 23 patients showed a rapid progress of the disease. Therefore, HCV-infection cannot be considered any longer as a disease that is primarily transmitted parenterally. Due to the large number of sporadic infections, HCV-infection will continue to be of great epidemiologic importance even after the effective elimination of contaminated blood products.