To assess the efficacy of interferon (IFN) combined with a large dose of glycyrrhizin (SNMC) therapy in patients with chronic hepatitis C who were resistant to interferon therapy alone, we studied 8 patients with chronic hepatitis C who did not respond to the initial interferon therapy. Initially all of 8 patients received 6 million units of alpha-IFN intramuscularly, three times a week, for 3 months and their serum alanine transaminase (ALT) did not decrease more than 50% at the end of therapy and returned to pretreatment levels after therapy. Six months later, all of these patients received alpha-IFN (6 MU) combined with 80 ml of SNMC intravenously, three times a week for 6 months. Prior to the initial IFN therapy alone, all of the patients were positive for anti-HCV and HCV RNA in the serum. With IFN therapy, serum HCV RNA became negative in 4 of 8 patients and HAI score decreased significantly although their ALT levels did not decrease more than 50%, while with IFN combined with SNMC therapy, ALT levels decreased approximately 70% in all patients (one became normal), serum HCV RNA became negative in 2 and HAI scores did not change significantly. There was no significant differences in decrease of HCV RNA titers and HAI scores between two therapy except the ALT levels. These findings suggest that IFN combined SNMC therapy does not appear to be more beneficial than IFN therapy alone.