The cardiac output,1 the circulating blood volume,2 the velocity of blood flow, the pulse rate, the pulse pressure and the vital capacity3 are decreased when the basal metabolic rate4 is low in patients with myxedema. The pale, cold, dry skin of patients suffering from this disease suggested that there might be alterations of peripheral blood flow. Objective measurements, however, are not contained in the literature relating to the amount of blood allocated to the periphery. Stewart and Evans5 found that the peripheral blood flow in patients with hyperthyroidism was increased and that it fell with the administration of iodine and decreased further still after subtotal thyroidectomy, so that there was a linear relation between basal metabolic rate and peripheral blood flow. The increase in peripheral blood flow accounted for the pink, moist skin which these patients exhibited. It was of interest to measure the peripheral