Recombinant alpha-interferon (IFN-R) was given to 17 patients with non-A, non-B chronic hepatitis (NANB-CH) and to 11 patients with B chronic hepatitis (B-CH). Fever (100.4 to 102.2 Fahrenheit) was observed in every patient during the early phase of treatment. Other side-effects included rigors, myalgia, headache and laboratory changes such as leucopenia, neutropenia and, in some cases, thrombocytopenia. However, the tolerance was considered acceptable and treatment had to be interrupted in only one patient presenting generalized mucosal lesions attributed to a hypersensitivity reaction. The response to IFN-R in NANB-CH was considered positive when serum aminotransferase levels became normal or below two times the upper normal limit. Out of eight patients who completed the treatment, four were considered as responders but one of them, treated during five months, showed a relapse after three months. On the other hand, in one patient treated for twelve months, a persistent normalization of serum amino-transferases was observed: a liver biopsy showed a striking decrease of the inflammatory changes. As to the B-CH. 3 out of 8 patients who completed the treatment showed a disappearance of HBeAg and DNA-polymerase and were considered as responders. These preliminary results show that IFN-R is a promising drug but only multicenter controlled trials will establish its value in the treatment of viral chronic hepatitis.