To determine the effect of a recombinant alpha interferon 2b (Intron-A) and possible benefit of prednisolone pretreatment in chronic non-A, non-B hepatitis, 75 Chinese patients with clinico-histologically proven chronic hepatitis were randomly allocated to one of the following regimens: (A) 3 million units of Intron-A trice weekly for 6 months; (B) dose titration according to ALT-AST values; (C) prednisolone withdrawal followed by regimen A; (D) control group: no treatment for 6 months but followed by alternating treatment with 3 million units of Intron-A trice weekly for 2 weeks followed by 2 weeks no treatment for 6 months. Up to September 30, 1990, 67 patients have been followed for a minimum of 2 months. At the end of the second month, complete response (normal ALT) was achieved in 71% of group A, 50% of group B, 50% of group C and 0% of group D. At the end of the 6th month, the complete response rate was 62%, 47% and 64% respectively in groups A, B and C. The response rates in groups A and C were significantly better than the 7% in the control group. Complete response usually (91%) occurred within 2 months after the first dose of interferon. Relapse occurred in 40% of the complete responders, usually within 2 months of the last dose. The cumulative relapse rate was significantly lower in responders of group C (11% vs 43% in group A and 86% in group B during a period of 6 months). Only mild adverse effects were reported though two patients withdrew because of intolerable fatigue.(ABSTRACT TRUNCATED AT 250 WORDS)