Intraarterial administration of urokinase using Tracker microcatheter was performed in 11 patients with acute cerebral infarction caused by embolic occlusion of the internal carotid or the middle cerebral artery. Recanalization was observed in seven cases (64%) following the fibrinolytic therapy, and the time until recanalization from the start of the treatment was on the average 2.8 hours. Recanalization was seen in five out of six cases that received superselective infusion of urokinase, while it was seen in two out of five cases that received selective infusion. This study suggests that superselective infusion of urokinase is an excellent therapeutic method for embolic occlusion of the cerebral artery.