Transcranial Doppler ultrasonography (TCD) is a noninvasive, bedside, portable tool for assessment of cerebral hemodynamics. Modern TCD head frames allow continuous hands-free emboli detection for risk stratification and assessment of treatment efficacy in several cardiovascular diseases. Identifying a focal stenosis, arterial occlusion, and monitoring the treatment effect of intravenous tissue plasminogen activator can easily be accomplished by assessing TCD waveforms and determining prestenotic and poststenotic mean flow velocities. TCD is an excellent screening tool for vasospasm in aneurysmal subarachnoid hemorrhage. The use of intraoperative TCD during carotid endarterectomy and stenting allows optimal intraoperative hemodynamic management. Other applications are also discussed.