The problem of development of diabetic myocardiodystrophy is analyzed. Thirty-seven patients with type 1 diabetes running a grave course with various disease duration were examined. The major parameters of intracardiac hemodynamics were examined by echolocation; exercise tolerance was studied by bicycle ergometry. The data indicate the development of diastolic rigidity, reduced volume of leftventricular myocardium, and decreased stroke and minute output at the early stages of the disease. Bicycle ergometry showed reduced exercise tolerance. These changes were in direct proportion to disease duration, presence of microangiopathy, and compensation status. These parameters may appreciably improve in recovery of the disturbed metabolic processes with restoration of the age-specific norm in patients with not long disease standing. Hence, echolocation of the heart and bicycle ergometry may be regarded among the criteria of diabetes mellitus compensation.