Our purpose was to evaluate the clinical indications for carotid duplex ultrasonography and determine for each indication how often carotid artery disease was identified.We retrospectively reviewed the consecutive reports for 3191 carotid ultrasound examinations. We tracked 14 indications to determine how often examinations were requested for each indication and correlated each indication with the finding of carotid artery disease.We found 26.5% of all examinations were abnormal; 17.5% of patients showed internal carotid artery disease; 10.9%, a moderate stenosis; 5.2%, a severe stenosis; and 1.4%, a total occlusion. For each of the 14 individual indications, with 1 exception, carotid ultrasound examination showed a 19.7% or greater chance of an abnormal result and an 11.6% or greater chance of finding a flow-limiting stenosis of an internal carotid artery.Our results validate the collaborative position of the American College of Radiology, the American Institute of Ultrasound in Medicine, the Society for Pediatric Radiology, and the Society of Radiologists in Ultrasound that, overall and for almost all indications they enumerate, carotid ultrasound examinations are a proven and useful procedure for evaluating extracranial carotid artery disease.