With substantial effort and research devoted to improving surgical techniques and myocardial protection, superb results have been achieved for repair of complex congenital heart defects in children. As a result, investigative efforts now have begun to examine the quality of life for patients surviving these operations. Because these neonates and infants are exposed to severe physiologic extremes of temperature (15–18 °C) and severe alterations from normal perfusion (total circulatory arrest), the nature of long-term neuropsychological outcome has been a prominent concern. Recent preliminary reports suggest that transient and permanent neuropsychologic injury occur in as many as 25% of all infants undergoing hypothermic cardiopulmonary bypass with circulatory arrest.'Since improved surgical techniques have significantly reduced rates of operative mortality and cardiac morbidity, one of the greatest risks remaining for the patient with congenital heart disease may be long term neuropsychologic and developmental abnormalities.