The very important role of echocardiography in the prac¬tice of cardiology has been outlined above. There is one important diagnosis, however, that the echocardiogram is not able to resolve adequately. The obstruction of coronary arteries by atheroma, which causes angina and fatal and nonfatal heart attacks and accounts for more than 90% of deaths from coronary artery disease cannot be visualized with this technology. Intravascular ultrasound done at the time of interventional procedures is improv¬ing our knowledge of the atherosclerotic process and its complications, but this technique cannot be applied in clinical practice.