The results of the examination of 20 patients having chronic hepatitis delta (CHD) with the disease lasting 1-2 years (8 patients) and 3-6 years (12 patients) are presented. In most of the patients of both groups, irrespective of the duration of the disease, the development of severe hepatic lesions has been established. The morphological study has revealed in 45% of the examined patients the presence of chronic active hepatitis leading to the cirrhosis if the liver. A prolonged course of treatment (8-12 months) with reaferon (recombinant interferon alpha 2, obtained by gene engineering technique), injected intramuscularly in a dose of 1 x 10(6) I.U. once or twice a week, has proved to be effective in 47% of CHD patients aged 15-30 years with a weak expression of autoimmune process. It is recommended that interferon therapy in patients with CHD requires individual indications.