We studied 882 cases of isolated ventricular septal defect (VSD) diagnosed from 1971 to 1988 with a mean follow-up period of 9.5 years. They represent 22.5% of all congenital heart defects diagnosed in this period. Six hundred eighty-three children (77.4%) did not develop symptoms, had small defects, and the rate of spontaneous closure was high (40.2%). The remaining 199 children presented symptoms; at the initial catheterization 25, 65, 107, and 2 cases were grouped in hemodynamic groups 2, 3, 4, and 5-6, respectively, on the basis of pulmonary flow and resistance. Only seven patients (0.7%) developed aortic regurgitation, and only five patients (0.5%) developed infective endocarditis. Complete surgical correction was performed in 137 children (15.5% of the total cases), with surgical mortality decreasing from 21.4% before 1983 to 3.5% afterward. Overall mortality was 3% for the entire cohort, 0% for hemodynamic groups 1 and 2, 3% for group 3, and 25% for hemodynamic groups 4-6. About two thirds of the deaths took place between 1 month and 1 year of life, and one thirds of the deaths occurred before surgical treatment. Surgical mortality rates for hemodynamic groups 2, 3, and 4 were 0, 4.7, and 15.3%, respectively. Actuarial survival curves show an important improvement in the prognosis after 1983. Our results stress the importance of early surgical complete correction on patients with large defects and severe hemodynamic changes.