THE INCIDENCE of congenital heart defects is approximately 7 to 10 per 1,000 live births. With advancing technology and improved diagnostic, surgical, anesthetic, and postoperative management protocols, the tendency today is to perform the complete repair of defects early in infancy. Infancy is defined as the period from birth until age 1. The management of cardiopulmonary bypass (CPB) in infancy has many challenges and increased risk of morbidity and mortality compared with that of the adult population. Infants are more prone to complications because of the immaturity of their organ systems. There is a need for a more complete understanding of the anatomic, metabolic, and physiologic differences between infants and adults, and patient care must be individualized considering the degree of hemodilution and hypothermia, acidbase strategies, flow rates, circuit designs, priming the pump, and choice of cannulae. This review article outlines the differences between infants and adults regarding their responses to CPB and reviews the main subjects like hypothermia, hemodilution, acid-base strategies, inflammatory response, extracorporeal circuit, and CPB protocols for infants. Since the first successful application of extracorporeal circulation in the 1950s, CPB has evolved and still is evolving, but basic concepts have remained the same: Oxygenation and carbon dioxide elimination, perfusion, systemic cooling and rewarming, and removal of blood from the heart to provide a blood-free surgical field. On the other hand, despite clear understanding of the basic concepts and many improvements, CPB management in infants still remains challenging and unique.