Transcranial Doppler US, a non-invasive tool for evaluating the cerebral arteries, has evolved significantly during the last two decades. This review describes the practical procedure, and summarises and illustrates its established and "work-in-progress" indications in children. Indications for a transcranial Doppler US examination include, but are not limited to: (1) evaluation of cerebral blood flow velocities in the circle of Willis in patients with sickle cell anaemia to guide transfusion therapy; (2) diagnosis and follow-up of vasculopathy, such as moyamoya disease; (3) diagnosis and monitoring of acute cerebrovascular disorders in intensive care patients, in particular following traumatic brain injury, and during cardiovascular surgery; and (4) confirmation of a clinical diagnosis of brain death by documentation of cerebral circulatory arrest.