We studied by preoperative and postoperative catheterization 162 unselected patients having surgical closure of ventricular septal defects; 135 patients (83%) had completely closed defects, and 27 patients (17%) had residual shunts. Almost uniform reduction of the preexisting elevated pulmonary pressures and reversion to a normal pulmonary flow were consistent findings. Approximately 93% of the patients with closed defects were asymptomatic, compared to only 15% who were asymptomatic preoperatively. A postoperative systolic murmur may be compatible with complete closure, but a persistent systolic thrill usually indicates a residual shunt. Periodic postoperative recatheterization in eight patients with significant pulmonary vascular disease prior to closure indicated that seven have improved progressively over the years studied. Only two patients in this entire group of 162 showed a progression in their pulmonary vascular disease following ventricular septal defect closure.