The role of contrast-enhanced computed tomography (CT) was evaluated in three nonhuman primates with a severe cerebrovascular insult and resulting elevated intracranial pressure and diffuse circulatory arrest. In all three animals the brain vasculature did not opacify after the bolus intravenous injection of iodinated contrast media. In addition, the brain substance did not enhance although the arterial blood enhanced normally after inhalation of a high concentration of xenon. Xenon-enhanced CT scanning, like 133Xe radionuclide scanning, may be used to define the absence of generalized cerebral perfusion.