Forty-seven patients with autoimmune chronic active hepatitis in remission on azathioprine and/or prednisolone were entered into a randomized controlled trial to assess the value of azathioprine alone in maintenance of remission. The trial design involved administering azathioprine at a dose of 2 mg per kg to one-half of the patients, in whom prednisolone was then gradually withdrawn, whereas the remaining patients, the "control" group, were maintained on the conventional combination regimen of azathioprine (1 mg per kg) with prednisolone. At 1 year there was no significant difference in respect of standard liver function tests or histological appearances between the two groups. Two patients in the azathioprine group required dosage reduction because of myelosuppression and both subsequently relapsed. Following withdrawal of corticosteroids Cushingoid features were lost with a return of weight and blood pressure to normality. In 75% of the patients, corticosteroid withdrawal was marked by arthralgias and myalgias which lasted for up to 12 months: no other major side effects of corticosteroid withdrawal were noted. Thus in the majority of cases, remissions in autoimmune chronic active hepatitis which are induced by corticosteroids can be maintained with azathioprine alone.