A total of 80 patients, diagnosed by echocardiography as having ventricular septal defect with aortic valvar prolapse, underwent cardiac catheterization and surgery. Echocardiographic and angiographic results were compared with surgical findings. The ventricular septal defects as observed during surgery were found to be doubly committed and subarterial in 49 (61%), muscular outlet in 10 (13%), and perimembranous in 21(26%). The location had been erroneously categorized by echocardiography and angiography in 12 (15%) and in 15 (19%) patients, respectively. Prolapse of the right coronary leaflet of the aortic valve, as documented by echocardiography, was confirmed by angiography in all but two cases. Prolapse of the noncoronary leaflet was detected by both imaging modalities in three patients. Prolapse of the right coronary and noncoronary leaflets was observed at surgery in 49 and three patients, respectively. The mean size of the ventricular septal defect, when measured by echocardiography, was significantly smaller than that found following surgical measurements (3.3±1.3 vs 8.4±3.8 mm, p<0.001). Our study showed that the ventricular septal defect was erroneously classified in the presence of prolapse of the aortic valve in 15% and 19% of our cases by echocardiography and angiography, respectively. The herniated sinus of Valsalva forming the “roof” of the ventricular septal defect probably redirected the jet across the defect to cause the errors in interpretation. Echocardiography, nevertheless, is as reliable as angiography in our hands in the follow-up of patients with ventricular septal defect opening to the outlet of the right ventricle.