Transcranial Doppler sonography provides information on the velocity of blood flow in the major intracranial arteries and its direction in relation to the ultrasound probe. It is a non-invasive, inexpensive, easy, and repeatable method and can be performed at the bedside. It provides useful information on cerebral circulations, changes in the intracranial pressure, on the diagnosis of patent foramen ovale, and in the evaluation of risk factors for stroke. Other indications include monitoring of intracranial arterial occlusions and stenosis, detection of emboli, and assessment of cerebrovascular reactivity.