Fifteen patients with chronic type B hepatitis were treated with corticosteroids in a randomized, double-blind, placebo-controlled trial lasting 28 days. Ten patients received prednisolone, 60 mg/d for 2 weeks, then 30 mg/d for another 2 weeks; 5 patients received placebo. Serum aminotransferase levels decreased significantly during prednisolone therapy but 4 to 10 weeks after abrupt withdrawal of the drug, they rebounded to levels greater than those before treatment. This exacerbation of disease lasted for several months and was prolonged and symptomatic in 3 patients. Hepatitis B virus levels did not change substantially during treatment. Follow-up examinations showed no improvement in biochemical or serologic features of the disease in any of the 15 patients; follow-up liver biopsies showed a worsening in 4 of 7 treated patients but in 0 of 5 control patients. Thus, a 28-day course of prednisolone produced no beneficial effects in patients with mild-to-moderate chronic type B hepatitis; on the contrary, such treatment may be harmful.