With the aid of Xe133 injected into the anterior tibial muscle a study was made of the state of muscular circulation in 50 patients with decompensated diabetes mellitus and in 23 patients after the compensation of the disease was reached. There was a marked reduction of the muscular circulation in the majority of the patients at rest and also a fall of the adaptive possibilities of the vessels in response to the physical loading under conditions of artificially induced ischemia. Compensation of diabetes against the background of complex therapy (vasodilating, antisclerotic, lipotropic agents, polyvitamins, potassium salts) promoted but an insignificant improvement of the circulation at rest. The extent of disturbances of the muscular circulation depended on the severity, the character of the course of the disease, the patient's age, and the presence of vascular affections. Adaptive possiblities of the vessels in diabetic patients became more pronounced with the development of hypertension. The character of diabetes treatment produced no significant influence on the extent of the circulatory disturbances in the muscles.