BACKGROUND Microvascular bleeding after Cardiopulmonary bypass (CPB) is mainly due to consumption of clotting factors, platelets damage, and hyperfibrinolysis. Aprotinin, the only antifibrinolytic drug effective in preserving platelets, is no longer available; an alternative regimen based on pure antifibrinolytic drugs has been proposed, since hyperfibrinolysis is known to contribute both to clot lysis and platelet dysfunction. In this study the efficacy of two antifibrinolytic drugs, Tranexamic acid (TA) and epsilon-aminocaproic acid (EACA), was tested in patients undergoing cardiopulmonary bypass (CPB), for primary myocardial revascularization. METHODS Forty-eight consecutive patients were randomized to receive prophylactically equipotent doses of EACA (group A) or TA (Group B). Platelet count, prothrombin time, fibrin digestion products, blood loss and transfusion requirements recorded after 6 and 24 hours from the end of surgery were compared. RESULTS The two groups were comparable for length of CPB and numbers of grafts; no significant difference was observed in the coagulation parameters considered. Blood losses were less in group B (TA) than in group A (EACA), both at 6 and 24 hours after surgery; homologous blood transfused was also less in group B, but no difference was statistically significant. No adverse effect was observed. CONCLUSIONS In coronary patients, TA and EACA exhibit the same effects on blood loss and requirements after CPB; either drug can be safely used in cardiac surgery.