Doppler sonography, combining high-resolution imaging and Doppler spectrum analysis, has proven to be the best choice for safe, noninvasive, low-cost screening for the etiology of stroke. With high-resolution imaging, plaque can be characterized relative to the risk for intraplaque hemorrhage, thought by many to be the precursor of plaque ulceration. Using high-resolution ultrasound, heterogeneous plaque has been shown to be associated with intraplaque hemorrhage. Criteria for distinguishing heterogeneous from homogeneous plaque are discussed, as are techniques for characterizing plaque. Several published articles strongly suggest that, when heterogeneous plaques are identified, the incidence of neurological symptoms and stroke on follow-up increases, relative to patients with homogeneous plaques. Additional long-term follow-up studies of heterogeneous plaque are needed. Most recently, carotid wall thickness has been evaluated as a physiological marker for atherosclerotic disease and as a gauge of the effectiveness of medical therapies. It is likely that carotid wall thickness will become important in the diagnosis and management of atherosclerosis. Radiologist are encouraged to learn this new form of ultrasound examination, which is reviewed briefly in this article.