The greatest advances in understanding and treating stroke have occurred during the past 30 years. The advantages of ultrasound for vascular diagnosis are well known : it is a fast, portable, non-invasive, repeatable and inexpensive technique. Among various clinical situations for the application of ultrasound to stroke care, the best established ones include : ① early detection and characterization of extracranial atherosclerosis and occlusive diseases especially at the carotid bifurcation ; ② evaluation of consequences of proximal arterial occlusive disease on the distal cerebral vasculature ; ③ follow-up of the natural history and response to treatment of acute arterial occlusion that causes hyperacute stroke ; ④ detection of microemboli associated with cardiac and aortic pathology and carotid artery surgical manipulation ; and ⑤ follow-up of the time course and reversibility of cerebral vasospasm after subarachnoid hemorrhage. The field of ultrasonic diagnosis also has detractors and limitations. Even now, the technique is 'operator-dependent'in terms of the accuracy and validity of its results. Newer technology has provided significant advances in this regard ; however, it is necessary for each laboratory to maintain a strict quality control in order to maximize the benefits that this powerful technology can provide.