We reviewed the records of 66 patients who underwent cardiopulmonary bypass; half of these patients received the plasmin inhibitor, tranexamic acid. The demographics were not different between the group who received tranexamic acid and the group who did not (control group). There was no difference in the heparin or protamine requirements between the two groups. There was a significantly greater amount of 12-hr chest tube bleeding in the control group (495 +/- 484 vs. 863 +/- 655 in the control and tranexamic acid groups, respectively; p < .02). There was no difference between the groups in either the post-operative hematocrit, platelet count or the number of patients requiring transfusion. Although tranexamic acid decreased the amount of chest tube output, there was no demonstrable patient benefit derived from its use.