Transcranial Doppler (TCD) provides lots of information of cerebrovascular system and is widely used to diagnose the intracranial stenosis, and vasospasm of subarachnoid hemorrhage. But magnetic resonance angiography (MRA) and computed tomography angiography (CTA) are not only standard diagnostic tool and also more useful studies than TCD in the diagnosis of intracranial stenosis because of the accuracy, popularity of machine and the coverage of medical insurance. But TCD has the strong point in understanding cerebral hemodynamics and monitoring. And sonothrombolysis is the new field of TCD for increasing the recanalization rate of thrombolysis of acute ischemic stroke. Therefore the author would review the clinical application of TCD on acute ischemic stroke, sonothrombolysis, monitoring with emboli detection, vasoreactivity test and so on. Journal of Neurosonology 2(1):10-13, 2010

Key Words: Transcranial Doppler, Acute ischemic stroke, Sonothrombolysis, Monitoring, Vasoreactivity