ObjectiveTo search for the effect and safety of urokinase (UK) in different dosage on acute cerebral infarction.Methods80 patients suffering from acute cerebral infarction were randomly divided into two groups. Group A received UK 0.75 MU intravenously within 30 min. Group B received UK 1.0～1.5 MU intravenously within 30～45 min. ResultsThe neurological deficits scores was improved in both groups. There was no significant difference between group A and group B(P>0.05). The total effective rate and significant effective rate was 82.5% and 60.0% in group A respectively, but those were 87.5% and 65.0% in group B respectively(P>0.05). More hemorrhage happened in group B. ConclusionThe UK in small dosage is effective and relatively safe in treatment of acute cerebral infarctions.