Patients with atherosclerosis who have had conventional angiography at Suburban Hospital in Bethesda, MD, may be considered for this study. They will be screened with a brief history and physical examination, and those enrolled will have a MRA scan within 72 hours of their conventional angiogram. For this procedure, a catheter is placed in a vein in the patient's arm and the patient lies on a table that slides into a magnetic resonance imaging (MRI) scanner-a large donut-shaped machine with a magnetic field. Surface coils-flexible, padded antennae used to improve the quality of the pictures-are wrapped around the patient's legs. At times during the scan, the patient is asked to hold his or her breath for several seconds, and a contrast material called gadolinium is injected through the catheter in the vein. This substance enhances the images of blood flow in the vessels. The procedure generally takes about an hour and a half, although the actual imaging takes only a small part of that time.