In the performance of open-heart surgery, a low-prime oxygenator is desirable. This solves problems associated with blood procurement and reduces reactions resulting from multiple blood transfusions. Neptune1 was the first to utilize acid citrate bank blood (ACD) and isotonic saline in priming his system. Zuhdi,2 Long,3 DeWall,4 and Cooley5 have performed intentional hemodilution perfusion using either low molecular weight dextran (LMWD) or 5% dextrose in water as priming material. The oxygenators used by these groups were variations of the basic bubble oxygenator. The rotating disc oxygenator which, in our hands, has proved hematologic advantages, however, can also be used with a low priming volume. This is accomplished by incorporating a Gebauer internal heat exchanger in the oxygenator and using LMWD and ACD blood for priming the extracorporeal circuit. The purpose of this communication is to describe our experiences in using this system in the performance