The therapeutic strategy of the left main disease is quite different frorn usual coronary artery disease. Therefore, the diagnostic evaluation should be done carefully. Eventhough coronary angiography has been considered as a gold standard for the diagnosis of left main disease, its diagnosis is not possible in all cases. In questionable situation, direct visualization of the left main coronary artery and Doppler measurements of coronary blood flow by transesophageal echocardiography may give some diagnostic aids. We report a case of suspected isolated ostial left main stenosis, which was helped diagnotically by perfoming transesophageal Doppler echocardiography.