The present study was aimed to test the efficacy and safety of interferon alpha (Wellferon-Wellcome Foundation Ltd.) either alone, or in combination with short-term corticosteroid pretreatment in the therapy of chronic hepatitis B. 44 patients with documented chronic hepatitis type B (12 women and 32 men; mean age 37.5 years, range 23-59 years) and satisfying the entry criteria were subjects of the study. 30 patients had chronic active hepatitis on liver biopsy, while 14 had chronic persistent hepatitis. Consecutive patients were given either placebo or prednisone in a double-blinded manner for 4 weeks (0.6 mg/kg/day in the first two weeks, 0.45 mg/kg/day in the third week and 0.25 mg/kg/day in the last week), and then, after a 2 week pause, therapy with interferon was instituted for a total of 12 weeks. Interferon was given by intramuscular injection in a single daily dose of 10 x 10(6) IU for 5 days and three times weekly thereafter. However, because of side effects, the dose of interferon was occasionally reduced to 5 x 10(6) IU in most patients. Interferon induced a sustained cessation of HBV replication as judged by loss of DNA-polymerase activity in 26 (59%) patients, 20 (45%) patients seroconverted to anti-HBe. Additionally, 6 (14%) cases lost HBsAg and seroconverted to anti-HBs. Prednisone pretreatment did not seem to improve the efficacy of interferon therapy. The outcome of the treatment was unrelated to gender and pretreatment activity of transaminases, however, patients with low activity of HBV replication were more likely to respond to therapy than patients with high HBV replication.