Capotene is an effective drug for preventing and treating diabetic myocardiodystrophy. A two-month capotene therapy (12.5 mg daily) was carried out in 20 patients with IDDM aged 12-18 years with disease of different duration without clinical signs of cardiac insufficiency, with echocardiographic changes typical of diabetic myocardiodystrophy. Eight patients were administered 3 similar courses with 6-month intervals. The major hemodynamic parameters were investigated by echolocation, and exercise tolerance was evaluated by bicycle ergometry. The data indicate the efficacy of capotene therapy in patients with diabetic myocardiodystrophy, particularly of repeated courses, carried out under conditions of compensated carbohydrate metabolism. The diastolic parameters improved in comparison with those in patients administered no capotene; myocardial contractility and exercise tolerance increased. Capotene therapy did not involve changes in insulin protocols.