Aortic valve prolapse (AVP) was detected in 82 (7.5%) of 1096 patients with ventricular septal defect (VSD) (in 50 at initial echocardiographic examination and in 32 at follow-up) by echocardiography. Of 82 patients with AVP, aortic regurgitation (AR) was detected in 53 (65%) (in 28 at initial echocardiographic examination and in 25 at follow-up), resulting in an incidence of AR of 4.8% (of VSD). The percentage of AVP (20.8%) and AR (16.7%) in muscular outlet VSDs was larger than the percentage of AVP (10.6%) and AR (6.8%) in perimembranous VSDs (p < 0.05). Fourty-four patients were followed medically after AVP appeared (3 months to 10.8 years; median, 2.1 years). Initially, there was no AR in 24 of these patients, trivial AR in 7, and mild AR in 13. Trivial AR developed in 6 (25%) and mild AR developed in 3 (13%) of 24 patients who had no AR (in 5 of them within 1 year and in 9 of them within 2 years). In 2 (29%) of 7 patients, trivial AR progressed to mild AR during a median of 2 years, and in 4 (31%) of 13 patients, mild AR progressed to moderate AR during a median of 1.1 years. We recommend frequent echocardiographic evaluation (every 6 months) for detecting of appearance of AR in patients with perimembranous or muscular outlet VSD after AVP develops and for evaluating the progression of AR in patients with perimembranous or muscular outlet VSD, AVP, and trivial AR. In addition, we recommend surgical intervention in patients with perimembranous or muscular outlet VSD, AVP, and mild AR because of rapid progression of mild AR to moderate AR.