Long-term treatment with prednisone and azathioprine gives satisfactory results in chronic aggressive (chronic active) hepatitis. Of 18 patients treated between 1966 and 1976 for an average of 2.9 years the disease became inactive clinically, biochemically and histologically in 13; merely two continued to have minimal activity histologically. These patients have not required any treatment for two years (on average). In one patient there are still definite signs of activity and immunosuppressive treatment is being continued. Four patients died of cirrhosis of the liver: two of them had not taken the drugs conscientiously. Death occurred on average two years after the diagnosis had been made. Of the 18 patients five were positive for hepatitis-B antigen.