The cerebral hemodynamic action of Vincamine is measured in 17 patients with primary or secondary cerebral circulation disorders, by use of the multiregional 133Xe clearance technique. The statistical analysis of the results justifies the grouping of all the cases and the distinction between reference, ischemic and hyperemic zones by determining for each subject a range of + or –15% of his own mean regional cerebral blood flow. The drug, in a single injection in the internal carotid artery, shows a significant beneficial hemodynamic effect on the ischemic regions of the brain. No steal phenomenon is recorded in the middle cerebral artery territory. The action of the drug leads to a decrease and an equalization of the hemodynamic resistances of the cerebral vascular be