Of 59 patients with traumatic hyphema studied prospectively, 32 received aminocaproic acid, an antifibrinolytic agent, to prevent secondary hemorrhage. The remaining 27 patients received placebo in an identical manner. Of the aminocaproic acid-treated patients, only one (3%) rebled, while nine patients (33%) receiving placebo suffered secondary hemorrhage. The results of this study indicate a statistically significant reduction (P less than .01) in the incidence of rebleeding in patients treated with this drug.