The pediatric medical community has long been concerned about the increased incidence of cerebral dysfunction among newborns with severe cyanotic congenital heart disease. There has been concern about a great number of potential predisposing factors including the effects of hypoxemia and acidosis, trauma during cardiac catheterization, and the duration of prolonged decreased arterial oxygen saturation. Many infants undoubtedly undergo significant brain damage prior to surgery, but may be subject to further insult in the peri-operative period. The proposed trial studied circulatory arrest versus low-flow bypass methods of surgical support in a homogeneous group of patients who were managed in identical fashion in all other aspects of their treatment. Major factors, such as the influence of cardiac catheterization and presurgical status were specifically incorporated into the primary statistical analysis. This was important in order to identify significant predisposing causes of brain injury beyond the surgical techniques being compared, and to increase the power of the comparison.