Early recanalization is assessed using MR or CT angiography 4 to 8 hours after symptom onset. The evaluation of angiograms is performed by 2 neuroradiologists blinded to group of randomization and clinical details. The primary outcome measure is the rate of early recanalization. Recanalization is assessed using the TIMI classification. Secondary endpoints include the rate of symptomatic intracerebral hemorrhage, mortality, and functional outcome on the modified Rankin scale at 3 months.