We report a case acute lower extremity ischemia caused by emboli in which the initial diagnostic evaluation, including standard aortoiliofemoral arteriography and routine transthoracic two-dimensional echocardiography, failed to reveal the offending source. Because of the strong clinical suspicion that the origin of the arterial occlusion was embolic, transesophageal echocardiography was performed. Transesophageal echocardiography demonstrated an aortic valvular lesion and cardiac surgery was performed on an emergency basis. The use of transesophageal echocardiography in evaluating the heart and thoracic aorta as a source of distal emboli is also discussed.