To evaluate the histological effects of alpha Interferon (IFN) therapy, serial liver biopsy specimens from 30 patients with chronic hepatitis were studied. The biopsies were examined using a scoring system. After 12 mths of IFN therapy responders were 8 out of 11 HBV infected patients, 10 out of 12 HCV infected patients and only 1 out of 7 patients with cryptogenetic hepatitis. As spontaneous improvement of hepatic changes is infrequent, our data indicate that in terms of histological patterns interferon therapy is effective in chronic viral hepatitis.