A 25-year-old patient with a history of aortic stenosis due to presumed bicuspid aortic valve presented for elective aortic valve replacement. Intraoperative transesophageal echocardiography (TEE) revealed a trileaflet aortic valve but detected the presence of a subvalvular membrane. Multiplanar reconstruction of the 3-dimensional (3D) dataset measured a cross-sectional area of 0.8 cm at the level of this subvalvular membrane. Successful resection resulted in relief of the obstruction. Compared with preoperative transthoracic echocardiography, TEE was able to correctly characterize the nature of the stenosis with area determination accurately provided by application of 3D techniques.