Antifibrinolytic agents have been claimed to reduce the rebleed rate in patients with subarachnoid haemorrhage from intracranial aneurysms. However, these agents may in themselves increase the incidence of delayed cerebral ischaemia in these patients. We have used aspirin in an attempt to reduce the incidence of this complication. In a prospective, double-blind trial of aspirin against placebo, 53 patients with subarachnoid haemorrhage were all treated with the antifibrinolytic agent tranexamic acid. Twenty-seven patients received aspirin and 26 patients received placebo. The morbidity and mortality was similar in each group. A further breakdown into patients who had their aneurysms clipped at craniotomy (21 patients) similarly failed to show a more favourable outcome in either group. It is concluded that aspirin does not affect the outcome in patients with subarachnoid haemorrhage treated with tranexamic acid.