There have been several methods utilized in the diagnosis or assessment of medical or surgical treatments of peripheral arterial diseases. In this study, the diagnostic value of a new tracer: Tc-99m-methoxy-isobutyl-isonitrile (MIBI) has been demonstrated in patients with leg claudication. We successively performed muscle perfusion scans in 6 normals and 18 patients with claudication pain during rest and after exercise on the same day. Muscle perfusion abnormalities in all patients were consistent with the defects in the arteries of the affected limbs. The results show that this is a simple and accurate diagnostic procedure and superior to those that have been previously used.