THE PURPOSE of this investigation was to determine whether inappropriate fibrinolysis may be detected in the blood of patients with classical, sex-linked hemophilia (hemophilia A, factor VIII deficiency). The occurrence of spontaneous, unprovoked hemorrhage in many of these patients, without an actual change in the level of factor VIII, 1 suggested that an accessory defect in coagulation, such as excess fibrinolysis, might play a role in causing unpredictable bleeding. Furthermore, the availability of e-aminocaproic acid (EACA), an antifibrinolytic agent which has been used in the management of hemophilia, 2,3 indicated the need to document a rational basis for this form of treatment. Methods and Materials A total of 26 patients, ranging in age from 3 to 19 years, participated in the study. Five families were represented by two brothers each, and one family by three children. The remaining 13 patients were unrelated. Certain clinical variables were deliberately incorporated into the