The effects of silymarin (Legalon) therapy on liver function tests, serum procollagen III peptide level and liver histology were studied in 36 patients with chronic alcoholic liver disease in a six month double blind clinical trial. During silymarin treatment serum bilirubin, aspartate aminotransferase and alanin-aminotransferase values have been normalized, while gamma-glutamyl transferase activity and procollagen III peptid level decreased. The changes were significant, and there was a significant difference between post-treatment values of the two groups, as well. In the placebo group only gamma-glutamyl transferase values decreased significantly but to a lesser extent than that in the silymarin group. The histological alterations showed an improvement in the silymarin group, while remained unchanged in the placebo group. These results indicate that silymarin exerts hepatoprotective activity and is able to improve liver functions in alcoholic patients.