This study is a multi-institutional randomized double-blind placebo controlled trial of the use of glucocorticoids to improve the clinical course of neonates following cardiac surgery. Cardiopulmonary bypass (CPB) is critical to cardiac surgery, but the pathophysiologic processes engendered by CPB play an important role in post-operative recovery. The use, doses and schedule of glucocortiocoid administration to ameliorate these CPB induced processes is highly variable and without clear data to provide direction. The Primary Aim of this study is to compare the effects of intraoperative methylprednisolone to placebo on a composite morbidity-mortality outcome following neonatal CPB. Secondary Endpoints include: inotropic requirements, incidence of low cardiac output syndrome, fluid balance, ICU stay parameters, levels of inflammatory molecules, neuro-developmental outcomes, and safety parameters. The study will focus on neonates because their post-CPB clinical course is typically more severe, and that high level of severity itself provides a substrate for identifying the positive effects of a particular therapy. Finally, a therapy identified as beneficial has the greatest potential for benefit in this vulnerable population