Bleeding diathesis and allogenic transfusion after complex heart surgery, such as heart valve surgery, may result in complications such as transfusion reaction, viral infection, postoperative infection, haemodynamic disturbance, prolonged stay in the intensive care unit and hospital, renal and respiratory failure and mortality. In this prospective, double-blind, randomized, placebo-controlled clinical trial, 90 patients were randomly divided into three groups: aprotinin, tranexamic acid and control. Chest-tube drainage, transfusion requirements and renal and neurological complications were evaluated. We found that chest-tube drainage during the first (P < 0.0001) and second 24 h (P = 0.001) after admission to the intensive care unit were significantly lower in the aprotinin group. The amounts of transfused packed red blood cells (P < 0.0001) and platelets (P = 0.02) were significantly lower in the aprotinin and tranexamic acid groups. The quantity of transfused fresh frozen plasma (P = 0.034) was significantly lower in the aprotinin group only. We did not find any neurological complications or renal failure in the three groups. Our data suggest that in valvular heart surgery, low-dose aprotinin is significantly better than tranexamic acid or a placebo for reduction of postoperative bleeding and allogenic transfusion, without increasing adverse outcomes.