In a prospective consecutive non-randomised study including 1076 patients with ruptured intracranial aneurysms 205 patients received epsilon aminocraproic acid (EACA) and 871 did not. No significant differences between the two groups concerning clinical condition on admission, sex, age, localisation and size of the aneurysms were seen. No cases of rebleeding (RB) were observed within the first 4 days in the EACA treated patients, but within the first 48 hours, which is the optimal period recommended for operation of patients in good clinical condition, this difference of the rates of RB between EACA treated and not treated patients is not significant. A significantly lower rate of RB was observed in the EACA group within the first 2 weeks, but no significant differences in morbidity and mortality were found at the 2-year follow-up examination.