Supravalvular aortic stenosis is a rare cause of left ventricular outflow obstruction in adults. It occurs as an isolated defect sporadically or as a hereditary basis with an autosomal dominant trait without further phenotypical anomalies, or as a part of the Williams syndrome with mental retardation and multiple anomalies. In this report, we present a case of williams syndome associated with megacoronary artery.