Brain death can be characterized by cessation of cerebral blood flow. We have measured blood flow velocity in cerebral arteries of 17 comatous children with a transcranial pulsed Doppler equipment. In 11 children who progressed to brain death, we have recorded a progressive decrease of Doppler signal with the following steps: decrease of diastolic velocity, no diastolic velocity, reverse diastolic flow, decrease of systolic signal, no signal at all. In the 6 surviving children (all except one with severe deficits), after an initial reduction but never to a retrograde flow, arterial cerebral blood flow velocity increased to high diastolic values before normalization. Transcranial Doppler technique is non invasive, reliable, can be used at the bedside and repeated; it allows evaluating the cerebral blood flow in comatous children and represents a useful adjunct to brain death diagnosis.