The past few years have brought about a variety of techniques for direct-vision intracardiac surgery. External hypothermia was used first, but because of its limitations it has been largely replaced by other techniques. A disposable, autoclavable, simple, small-volume oxygenator with minimal destruction to blood elements would seem to most nearly meet the requirements of an ideal oxygenator.1 Because of flow-reservoir-oxygenation relationships, the combination of hypothermia and extracorporeal circulation may simplify the construction of such a heart-lung machine.2 A relatively small-volume apparatus for hypothermic total-body cardiopulmonary bypass will be described and its clinical application related. The priming of this system with 5% dextrose in water which is actually used for perfusion purposes will be stressed. Description and Method of Priming of the Heart-Lung Machine for Hypothermic Perfusion The system is a modified DeWall-Lillehei oxygenator and is depicted in Figure 1.3,4 The details of the design of the doublehelical reservoir heart-lung machine