Prognostic factors for mortality and recurrent hemorrhage in the preoperative, 2-week period were determined in 1114 patients who participated in the antifibrinolytic therapy investigations of the Cooperative Aneurysm Study between 1970 and 1977. Factors significantly related to mortality were admission neurological status, diastolic blood pressure, interval to treatment, degree of vasospasm, and medical condition. Factors associated with the likelihood of recurrent hemorrhage were interval to treatment, patient's sex, and admission neurological status. These factors need to be considered in the analysis of clinical data in the management of ruptured intracranial aneurysms.