The effects of intravenous tranexamic acid were compared with placebo in 64 patients with subarachnoid hemorrhage. A double-blind procedure was used. One gram of tranexamic acid was given intravenously every 4 hours up to the time of operation on an intracranial arterial aneurysm or for up to 21 days after the first bleeding if operative treatment was not feasible. There were no differences in re-bleeds, morbidity or mortality between the tranexamic and placebo-treated groups. No thromboemboiic complications were noted in either group. Our results do not support the use of tranexamic acid in subarachnoid hemorrhage in daily doses of 6 g.