A unicuspid aortic valve (UAV) is a rare congenital defect that may manifest clinically as severe aortic stenosis or regurgitation in the third to fifth decade of life. This report describes two cases of UAV stenosis in adult patients diagnosed by transesophageal echocardiography (TEE). The utility of three-dimensional TEE in confirming valve morphology and its relevance to transcatheter valve replacement are discussed.