Thirty-eight patients with chronic active hepatitis type B received antiviral therapy. In one trial, 22 patients were randomized to either no treatment or treatment with a 28-day cycle of adenine arabinoside 5' monophosphate (ARA-AMP); in a second trial, 13 patients were randomized to no treatment or treatment with two 28-day cycles of ARA-AMP separated by a 4-wk rest interval; during a third trial, 11 individuals were treated with 8 wk of prednisone therapy followed by 28 days of ARA-AMP therapy. The response rate (73%) to the regimen with prednisone was significantly greater than that achieved in the first or second trial (0% and 15%, respectively). The data indicate that the combination of short-term prednisone and ARA-AMP therapy may offer more promise for successful treatment of chronic active hepatitis type B than does ARA-AMP alone. Synergism may possibly occur by the combined effects of immune rebound provided by corticosteroid withdrawal and the inhibition of viral proliferation by ARA-AMP.