Selective brain cooling by irrigation combined with coronary perfusion and controlled cross circulation for the purpose of circulatory interruption during intracardiac correction under direct vision were studied on the standpoint of myocardial Ca and K metabolism in dogs. Following results were obtained. 1) Changes of the myocardial intake and output of Ca and K in the both methods were slight as in the routine thoracotomy at normal body temperature. They were found to be very useful methods is this regards. 2) However, in the use of low or moderate flow in these methods, and in combination of brain cooling with induced cardiac fibrillation or cardiac arrest, the changes in Ca and K levels were relatively marked. Therefore, it would be suggested that attentions should be pay to the pathological meanings of these Ca and K changes in the diseased heart.