In 6 cats, cerebral infarction was produced by transorbital occlusion of the left middle cerebral artery (MCA). Five animals developed typical cortical infarcts. Eight weeks later, cerebral blood flow (CBF) was determined by 14C-iodoantipyrine autoradiography and the number of intact neurons was counted histologically. Two non-operated cats served as controls. Cortical blood flow in the infarcted hemisphere was reduced by 24.6-74.4% when compared to the flow in the contralateral cortex and in controls. Averaged white matter flow was decreased by 39.1%. Regional cortical flow was gradually reduced from parasagittal regions towards the infarct. In the surrounding of the infarct, cortical perfusion was decreased to 24.8 +/− 9.7 ml/100 g/min, i.e. 19.7% of contralateral flow. Although the infarcts were sharply demarcated macroscopically, the number of cortical neurons decreased gradually from the midline to the peri-infarct zone. A significant linear correlation was found between absolute CBF-values and the number of neurons in areas of the infarcted hemisphere. The homolateral gyrus lateralis had normal neuronal density but flow was reduced by 20%. These findings suggest that the blood flow reduction in tissue surrounding chronic infarcts is due to neuronal cell loss and to functional inactivation caused by damage of afferent fibers.