Supravalvular aortic stenosis is relatively uncommon form of congenital heart disease and the most important lesion of this anomaly is various narrowing of the aortic lumen just above the sinus of Valsalva. We experienced a case of hourglass type of supravalvular aortic stenosis involving lcm from length from lcm above the sinus of Valsalva. The patient was associated with mental retardation, peculiar facies and dental anomaly. The diagnosis was confirmed preoperatively by retrograde left heart catheterization and left ventriculography. An incision was made in the ascending aorta and into the right coronary and noncornary sinus. Care was taken to protect the right coronary artery. A Y-shaped patch of Dacron was made to enlarge the stenotic portion of aorta. Postoperative pressure gradient between the aorta and left ventricle markedly reduced 36 mmHg in comparison with preoperative pressure gradient 150mmHg. The boy was discharged without any event.