A large meta-analysis of patients who have had a stroke with unknown time of onset with a DWI-FLAIR or perfusion mismatch showed that intravenous alteplase resulted in better functional outcome at 90 days than placebo or standard care. A net benefit was observed for all functional outcomes despite an increased risk of symptomatic intracranial haemorrhage. Although there were more deaths with alteplase than placebo, there were fewer cases of severe disability or death.