OBTAINING an adequate quantity of compatible blood for major surgical procedures in individuals with unusual blood groups and rare serum antibodies is a longstanding problem of blood banks and surgeons. Corrective cardiac surgery employing complete cardiopulmonary bypass and the disc oxygenator poses a particularly demanding example of this problem. Autologous blood in small quantities has been used clinically when anticipated blood requirements are minimal and the blood can be obtained from the patient within two to three weeks prior to surgery, this limit being imposed by conventional blood preservation methods. Recent advances in cryobiology and the preservation of blood in the frozen state at −85 C for prolonged periods of time suggested a new approach to the problem of major surgery in the rare blood group individuals. This report describes the successful use of frozen autologous blood alone during surgical correction on cardiopulmonary bypass of an interventricular septal defect with