Transesophageal echocardiography was performed in 34 patients before coronary angiography for suspected coronary artery disease to determine the usefulness in the detection of proximal left coronary stenosis. The control group consisted of 18 patients in whom coronaroangiography seemed to be negative. The diameter of the visualized coronary arteries, the systolic and diastolic peak flow velocities were measured. The left main coronary artery was visualized in 32 patients, the left anterior descending artery in 31 and the proximal part of the circumflexus artery in 23 patients of the coronary artery disease group, and in the same rate in the control group. The visualization of the right coronary artery was available only in 20-25% because of technical difficulties. The diastolic peak flow velocity over 60 cm/s in the left anterior descending artery reflected proximal stenosis with high sensitivity. In four patients transesophageal echocardiography was performed before angioplasty and after successful intervention. The high diastolic peak flow velocity significantly decreased in every patient. According to the observations the method can be used to perform morphologic and functional measurements on the left proximal coronary arteries.