In a retrospective study of the use of antifibrinolytic therapy in a series of patients with recently ruptured intracranial aneurysms, 131 patients were selected based on the following criteria: commencement of therapy within 3 days of the last subarachnoid hemorrhage (SAH); continuation of therapy for at least 6 days; and apparently uncomplicated surgery. Two main modalities of antifibrinolytic therapy were used: Group A, tranexamic acid (AMCA) 3 gm daily plus aprotinin k.i.u. (kallikrein inactivating units) daily (82 cases); Group B, AMCA 6 gm daily (41 cases). The remaining 8 patients were treated with epsilon-aminocaproic acid alone or in combination with aprotinin and were not considered to constitute a large enough group for statistical comparison. The rest of the preoperative treatment consisted of bed rest; mild sedation; antihypertensives, if the blood pressure exceeded 160 mm Hg; and osmotic diuretics as needed. The mean interval between last SAH and operation was about 13 days in both groups. The rates of rebleeding and thromboembolism were similar in the two groups but the rates of ischemic complications and post-SAH hydrocephalus were higher in Group B. The difference in the rate of severe cerebral ischemic complications was statistically significant (11 of 82 in Group A versus 12 of 41 in Group B, p less than 0.02), and in the main they were present preoperatively. The rates of rebleeding (approximately 10%) and of death from rebleeding (approximately 5%) are lower than in other published series on the natural history of this condition. In cases in which antifibrinolytics are indicated, present evidence indicates that low-dose AMCA plus aprotinin seems to be a rational combination for lowering the rebleeding, ischemic complication, and post-SAH hydrocephalus rates.