A double-blind clinical trial of tranexamic acid was carried out on 39 patients with fresh subarachnoid hemorrhage from a ruptured aneurysm. Twenty patients received tranexamic acid, 6 gm daily for 14 to 21 days, while 19 patients received conventional therapy of bedrest and dexamethasone when cerebral edema developed, plus isotonic saline. Rebleeding and mortality were reduced by one-fourth and one-fifth, respectively (p less than 0.001). No side-effects were observed. Tranexamic acid is valuable in the treatment of subarachnoid hemorrhage caused by ruptured intracranial aneurysms.