Ever since transplant surgery became a common procedure, the early diagnosis of irreversible cessation of cerebral function has become an important need. We made a comparative study of EEG, angiography and transcranial Doppler imaging in patients who fulfilled the clinical criteria for brain death. The imaging was performed with a 2 MHz pulsed Doppler system with a unique transcranial probe (EME, type TC2-64 B). Intracranial reverberating flow patterns with counterbalancing forward and backward components of the blood column indicate flow arrest. Transcranial Doppler Sonography was found to be a practical, non invasive, early and reliable method for the diagnosis of arrest of the cerebral circulation.