Both clinical and electroencephalographic criteria for brain death have limited value in the newborn. A simple test to determine the cessation of cerebral blood flow would be a useful adjunct to the determination of brain death in this population. In contrast to the invasive techniques used in older patients to estimate cerebral blood flow, the Doppler technique to estimate cerebral blood flow velocity from the anterior fontanelle of the newborn is noninvasive and can be used at bedside. In this study we define the changes in the flow velocity pattern in the anterior cerebral and the common carotid arteries in six newborn infants with clinical criteria for brain death: coma, absent brainstem function, and dependence on mechanical ventilation. A characteristic sequence of deterioration of the flow velocity waveform in both vessels was defined. This sequence consisted of (1) loss of diastolic flow, (2) appearance of retrograde flow during diastole, (3) diminution in systolic flow in the anterior cerebral artery, and, ultimately, (4) no detectable flow in the anterior cerebral artery, despite considerable flow in the common carotid artery. This constellation of findings suggests a progressive increase in cerebrovascular resistance and a progressive decrease in cerebral perfusion, compatible with the diffuse cerebral necrosis and edema documented postmortem. We conclude that the transcutaneous Doppler technique is a useful complement to other noninvasive methods, especially clinical assessment, in the determination of brain death in the newborn.