Background: To evaluate the clinical efficacy and safety of local intra-arterial thrombolysis with rt-Pa in patients suffering from MCA acute brain infarction within 6 hours of the onset of symptoms Material/Methods: Forty one patients with acute ischemic stroke of the middle cerebral artery (MCA) were qualified to the treatment (up to 6 hours after the beginning of the symptoms). Patient qualification was based on clinical examination, computed tomography (CT) and digital subtraction angiography (DSA). CT follow-up was performed after 24 hours and between 7-10 days. Continuous infusion of rt-Pa with a final dose of 40mg was administered. The patients were evaluated before, at discharge and 90 days after the procedure on the basis of modified Rankin and NIHSS scores. Results: At the primary outcome, 22 (53%) of the patients achieved modified Rankin scores of 2 or less after 90 days. The secondary clinical outcome at 90 day follow-up: (NIHSS score £1) - 9 (22%) of the patients, (NIHSS score ³50% decrease) - 24 (59%). A rate of recanalization was achieved in 76% of patients. Symptomatic hemorrhages occurred in 4 (10%). There were no deaths in the treated group after thrombolysis up to the time of discharge; however, the mortality during the 90-day follow-up period was 7%. Conclusions: Intra-arterial thrombolysis with the use of rt-Pa, in the treatment of ischemic brain stroke within 6 hours after the onset considerably improved the clinical condition of patients after 90 days