Fifty-five patients with a high-pressure, high-resistance ventricular septal defect underwent closure of their lesion. Twenty of the patients had had a previous pulmonary arterial band placed in infancy. There were 4 deaths among the 55 patients, an overall hospital mortality of 7.2%; 2 of the deaths (5.6%) occurred among the 35 patients who had primary closure of their ventricular defect and 2 (10%) occurred among the 20 patients who had had a previous banding procedure. Twenty-two patients were catheterized one year following primary closure of their ventricular septal defect. The pulmonary vascular resistance (PVR) decreased from a preoperative average of 1,475 to 480 dynes sec cm-1. Pulmonary artery mean pressure decreased from 74 mm. Hg preoperatively to 31 mm. Hg postoperatively. In 13 patients who had had previous pulmonary arterial banding, the mean PVR decreased from 1,920 dynes sec cm-5 before banding to 700 dynes sec cm-1 following banding. The mean PVR decreased further to 470 dynes sec cm-5 following closure of the ventricular septal defect and removal of the pulmonary artery band. Some of the patients had residual outflow gradients. We advocate primary repair of ventricular septal defect in symptomatic infants and elective correction within the first 3 years of life in patients with a large defect.