Vascular ultrasonography is now widely employed in the noninvasive screening of patients with atherosclerotic vascular disease. To date, radiologists have concentrated their efforts on the extracranial carotid arteries, but skills and technology developed in this area clearly have applicability elsewhere. Understanding of the physiologic parameters governing blood flow to the lower extremity is clearly useful in this day of interventional balloon angioplasty. There appears to be no single best test for noninvasive assessment of vascular disease, although each has its proponents and detractors. No single noninvasive technique described in this article appears to be a totally adequate screening test. Each has its strengths and limitations, but if one understands the different tests their complementary nature becomes clear. Utilization of a battery of noninvasive tests has been advocated, and various studies have suggested that when the results of two or more noninvasive tests agree, the diagnostic accuracy of that study increases significantly. In most noninvasive laboratories, at least two tests are performed, and in some noninvasive laboratories, as many as seven or eight tests are done. There is, of course, the danger that too much information may overwhelm the examiner, particularly when there may appear to be conflict among some of the test results. Furthermore, cost considerations and concern as to whether more is indeed better place realistic limitations on the number of studies that can and should be performed on any one individual. The choice of the most appropriate noninvasive tests for any single institution should be facilitated by a knowledge of the basic principles and strategies of vascular sonography outlined in this article.