In a prospective, randomized, double-masked study, 34 patients (34 eyes) with nonperforating ocular injury and traumatic hyphema were treated with either aminocaproic acid (Amicar), 100 mg/kg every four hours, up to a maximum of 30 g/d, or placebo for five days. None of 21 patients who were treated with aminocaproic acid rebled, while three (23%) of 13 patients who were treated with placebo rebled. This difference was statistically significant. Of the three patients who rebled, two required surgical intervention, with one patient requiring four surgical procedures. Although complications following aminocaproic acid therapy included light-headedness, nausea and vomiting, and systemic hypotension, only one patient was withdrawn from the study because of drug-related adverse reactions. This study strongly confirms that aminocaproic acid therapy significantly reduces the incidence of secondary hemorrhage following traumatic hyphema.