Using a scintillation camera system, hemispheric and regional cerebral blood flow was measured repeatedly during the course after a stroke. In 20 patients who improved clinically mean hemispheric and regional flow and relative weight of rapidly perfused compartment increased, while these values decreased in IS patients, on an average, whose clinical condition deteriorated or did not change. The changes of flow and relative weight were significantly different between the two groups. Furthermore, the relationship between changes in clinical condition, scored according to a rating scale, and changes in flow and compartmental weight was proved by significant Spearman rank correlation coefficients. In six cases hyperperfused areas in locations of disturbed neurological function were observed; these areas were found to be ischemic at measurements done early and late in the course after the stroke. This type of hyperperfusion was related to beneficial prognosis. The results indicate a shift of tissue from fast to slowly cleared compartment after a cerebrovascular attack. If tissue morphology is not entirely destroyed, recovery might occur; this results in an increas of recorded weight of rapidly clearing compartments, which correlates to the clinical course.