The surgical correction of congenital cardiac lesions that are complicated by intercurrent respiratory syncytial virus (RSV) pneumonitis has traditionally been deferred for at least 6 to 8 weeks. The presumption is that using cardiopulmonary bypass will increase the risk of postoperative pulmonary complications. We present an infant who developed acute respiratory failure related to RSV pneumonitis and required urgent mechanical ventilation. Cardiac evaluation revealed a large nonrestrictive ventricular septal defect (VSD), aortic arch hypoplasia, normally functioning bicuspid aortic valve, and hemodynamic instability associated with markedly increased pulmonary blood flow. Separation from mechanical ventilation was unsuccessful preoperatively. He underwent VSD repair with cardiopulmonary bypass less than 4 weeks after initial RSV infection. He was extubated successfully within 72 hours of VSD repair. Approximately 6 weeks postoperatively, he developed a circumferential chylous pericardial effusion of unclear etiology--an exceedingly rare complication of VSD repair in early infancy in a non-Down syndrome patient. The chylous effusion was initially managed unsuccessfully with Portogen/Monogen and a percutaneously placed pericardial drain. Two weeks later, he underwent creation of a pleuropericardial window with successful resolution of the chylous effusion. It is of interest to pediatricians to be able to correctly time the repair of congenital heart disease lesions after RSV infection to minimize post-bypass pulmonary complications and yet avoid morbidity from undue delays in repair. In addition, chylopericardium can occur in infants after VSD repair, and dietary modification and catheter drainage may not be adequate.