Left ventricular function was examined angiographically in 64 patients with ventricular septal defect and 13 postoperative patients with a preoperatively large shunt (postoperative group). The unoperated 64 patients were divided into three groups; small (left-to-right shunt ratio less than 35%), moderate (35%-50%), and large (greater than 50%). The control group consisted of 27 patients with Kawasaki disease. For assessing left ventricular function, left ventricular shape and the end-systolic wall stress to end-systolic volume index ratio, as well as left ventricular ejection fraction were examined. Left ventricular ejection fraction was higher in the small-shunt group (p less than 0.05) than in the control group, but normal in the other groups. Left ventricular end-diastolic shape was normal only in the small-shunt group and more spherical in the other groups. The large-shunt group alone manifested more spherical left ventricular end-systolic shape and lower end-systolic wall stress to end-systolic volume index (p less than 0.001). These findings suggest that the left ventricular dysfunction is present in patients with a left-to-right shunt larger than 50%, but this change was reversible in patients who underwent early repair of ventricular septal defect.