The purpose of this investigation was to determine the role of alcohol in development of progressive liver disease. For this purpose, 41 alcoholic patients were followed up for 5 years. Criteria for alcohol abuse was that the patients were enjoying 20 g alcohol daily in a period of 5 years for females and respectively 60 g daily for males. In the same time a group of 51 nonalcoholic patients with histologically proven chronic liver disease were investigated. In all 92 patients chronic liver disease and progression of the disease was proven by liver biopsy during a 5-years follow-up. In sera of all patients the markers of hepatitis viruses B, D and C were continuously determined and chronic viral hepatitis was excluded. Also, autoimmune chronic hepatitis was excluded. The results of the investigation showed that alcoholics develop cirrhosis hepatitis, in most cases 78.04%. The most progressive chronic liver diseases--cirrhosis and hepatocellular carcinoma--are significantly present among nonalcoholics (p < or = 0.05). In the mentioned investigation a large group of 51 patients with severe chronic hepatitis without a proven etiology of disease was found and it deserves priority in future research.