CT contrast enhancement of the ischemic infarction, blood-CSF barrier function for albumin, and severity of neurological symptoms were evaluated at predefined intervals in 41 patients with supratentorial ischemic infarctions. Contrast enhancement was most frequently observed in the 2nd and 3rd week after the stroke. This late CT enhancement was not related to infarction size and severity of blood-CSF barrier disturbance. The rare appearance of CT enhancement in the 1st week was usually associated with extensive infarctions and accompanied by blood-CSF barrier disturbances. These barrier disturbances, which occurred with higher frequency and greater severity in extensive infarctions (peak 3rd day), generally persisted for several weeks. We suggest that contrast enhancement in the 1st week after an ischemic stroke is due to diapedesis from necrotic capillaries; the more frequently observed late enhancement might be the result of a blood-brain barrier disturbance which in turn is hypothetically attributed to increased pinocytotic activity of regenerated endothelial cells.