The development of novel perfluorocarbon emulsions that contain higher concentrations of perfluorochemicals than previous emulsions has renewed interest in the use of this class of erythrocyte substitute in cardiopulmonary bypass (CPB). Perfluorocarbons have the potential to increase the oxygen content of the perfusate and thus increase the capacity of the heart-lung machine to deliver oxygen to the body during CPB.Increasing the capacity of the heart-lung machine to deliver oxygen to the body has important implications for the conduct of cardiac operations. For example, adding perfluorocarbons to the pump prime solution may allow larger volumes of blood to be withdrawn from the patient immediately prior to bypass for transfusion after bypass. Lowering the acceptable hematocrit during CPB with the use of perfluorocarbons may also decrease the need for homologous transfusions of erythrocytes in neonates or anemic adults who undergo CPB. © 1994, Informa UK Ltd. All rights reserved.