Transcranial Doppler (TCD) ultrasonography is the only noninvasive examination that provides a reliable evaluation of intracranial blood flow patterns in real-time, adding physiological information to the anatomical information obtained from other neuroimaging modalities. TCD is relatively cheap, can be performed bedside, and allows monitoring both in acute emergency settings as well as over prolonged periods; it has a high temporal resolution, making it ideal for studying dynamic cerebrovascular responses.To define the role of TCD in the evaluation of patients with acute ischemic stroke.We have analyzed the existing literature on the protocols for performing TCD in the evaluation of patients with acute cerebral ischemia. Extended applications of TCD in enhancing intravenous thrombolysis in acute stroke, emboli monitoring, right-to-left shunt detection, and vasomotor reactivity have also been described.In acute cerebral ischemia, TCD is capable of providing rapid information about the hemodynamic status of the cerebral circulation, monitoring recanalization in real-time and, additionally, has a potential for enhancing tissue plasminogen activator (TPA)-induced thrombolysis. Extended applications of TCD make it an important and valuable tool for evaluating stroke mechanisms, for planning and monitoring treatment, and for determining prognosis.TCD has an established clinical value in the diagnostic workup of stroke patients and is suggested as one of the essential components of a comprehensive stroke center. TCD is also an evolving ultrasound method with increasing diagnostic value and a therapeutic potential in cerebral ischemia.