✓ When the lateral striate arteries of the baboon are temporarily occluded for either 20 or 60 minutes, a near-cessation of blood flow is followed by a dramatic, transient local increase in blood flow values. These findings are evident from serial xenon (Xe)-computerized tomography (CT) measurement of cerebral blood flow (CBF). In this study, 20 minutes of vessel occlusion resulted in brief (< 1 hour) hyperemia, with no subsequent CT alteration and minimal random neuronal injury. Sixty minutes of occlusion resulted in a more prolonged hyperemia, a low-density area on CT images within 3 hours of reperfusion, and infarction of all cellular elements within the anterior lentiform nucleus. The Xe-CT method provides a sensitive, noninvasive technique for examining sequential alterations of CBF in small regions deep within the brain. This method of recording CBF also permits correlative studies of cerebral infarction, both clinically and experimentally, and allows reasonable inference about the probabilities of neuronal tissue damage with or without reperfusion.