To assess the ability of transthoracic high-frequency two-dimensional echocardiography to detect atherosclerotic lesions in the descending portion of the left coronary artery, 30 consecutive patients with suspected coronary artery disease underwent two-dimensional echocardiographic examination 24 to 96 hours before coronary angiography. The descending portion of the left coronary artery was arbitrarily divided into a mid segment (the portion of the coronary vessel embedded in the anterior interventricular sulcus) and an apical segment (the portion turning around the cardiac apex into the posterior interventricular sulcus). The mid segment was imaged in 24 and the apical segment in 25 of the 30 patients for a total of 49 out of 60 segments (82%). Comparison of the echocardiographically visualized segments with the corresponding angiographic segments indicated that a correct echocardiographic diagnosis of significant stenosis was made in 11 out of 12 segments. There were no false positive results. Thus the sensitivity and specificity of high-frequency transthoracic echocardiography in the detection of significant stenosis in the imaged segments were 92% and 100%, respectively. Compared with angiography, additional information concerning the status of the arterial wall, the presence of calcific plaques, and the cross-sectional extent of the obstructive lesions was obtained by echocardiography in eight patients.