Procedures related to profound hypothermia and circulatory arrest have produced a great improvement in the operative results of cardiac repair in neonates and infants. As we already obtained data on the effects of these procedures on cerebral metabolism, we focussed our attention on carbohydrate metabolism to determine whether or not cardiopulmonary bypass with pulsatile flow would improve the results of bypass method for core cooling and rewarming. In 12 mongrel dogs under conditions of hypothermia, plasma levels of glucose, insulin and glucagon as well as cortisol and noradrenaline were monitored in both pulsatile and non-pulsatile bypass groups. The hyperglycemia was significantly depressed and insulin levels increased in cases of pulsatile flow. Thus, even under conditions of hypothermia, pulsatile flow results in an improvement of the blood flow in the pancreas and there is a more extensive utilization of glucose and a greater protective effect on the function of the visceral organs during bypass.