Background: Patients with ischaemic stroke due to occlusion of the basilar or vertebral arteries may develop a rapid deterioration in neurological status leading to coma and often to death. While intra-arterial thrombolysis may be used in this context, no randomised controlled data exist to support its safety or efficacy. Methods: Randomised controlled trial of intra-arterial urokinase within 24 h of symptom onset in patients with stroke and angiographic evidence of posterior circulation vascular occlusion. Results: Sixteen patients were randomised, and there was some imbalance between groups, with more severe strokes occurring in the treatment arm. A good outcome was observed in 4 of 8 patients who received intra-arterial urokinase compared with 1 of 8 patients in the control group. Conclusions: These results support the need for a large-scale study to establish the efficacy of intra-arterial thrombolysis for acute basilar artery occlusion.