In a study of 60 patients with non-A, non-B/type C (NANB/C) chronic hepatitis alanine aminotransferase (ALT) activities returned to normal after treatment with interferon alfa-2b (3 million units for six months) in 70.7% and 29.3% did not respond. The response was maintained during four to six months, follow up in 41.4% of patients. Liver biopsy specimen showed histological improvement in all patients surveyed. Treatment was well tolerated with only mild side effects.