Over the past two decades, advances in equipment used for cardiopulmonary bypass and in operative techniques have resulted in a tremendous decrease in the mortality of patients undergoing surgical repair of congenital heart disease utilizing hypothermic circulatory arrest. Despite the widespread use of hypothermic arrest, opinion is not unanimous with regard to its safety. Previous studies which have examined neurological outcome following repair of congenital heart disease in infancy have generally agreed that when the period of arrest exceeds 60 minutes, there is increasing risk of cerebral injury.