It is known that patients with aortic stenosis, including those undergoing cardiac surgery for this problem, are prone to developing bleeding problems, particularly of the gastrointestinal tract. It is believed that the shear stress associated with blood flow through the abnormal aortic valve results in abnormal hemostasis. Abnormalities include increased proteolysis of the von Willebrand factor (vWF) and increased binding of the high molecular weight multimers of vWF to platelet membranes with subsequent inappropriate platelet aggregation. Thus, appropriate aggregation of circulating platelets is impaired. Cardiac surgery is associated with significant alterations in hemostasis. Patients undergoing cardiac surgery consume a significant percent of available blood products throughout the United States and are subjected to various and numerous risks associated with blood product transfusion. In addition, excessive postoperative bleeding is a common cause for the need to surgically re-explore the chest cavity in patients who have just undergone cardiac surgical procedures. Such additional surgery carries further cost and risk. Following surgical correction of aortic valve stenotic pathology, associated vWF abnormalities appear to reverse. However, this process can take several days. Although all cardiac surgical patients are at risk for postoperative bleeding, patients undergoing aortic valve surgery for aortic stenosis may be particularly at risk for this postoperative complication. In addition, patients with aortic valve stenosis who undergo noncardiac surgery may have a predisposition to bleeding because of similar underlying shear stress induced abnormal vWF and platelet function. The proposed study is a trial to evaluate the effectiveness of 2 different antifibrinolytic drugs in ameliorating the hemostatic defect associated with aortic stenosis. Aprotonin, an antifibrinolytic agent which also has platelet preserving actions4, will be compared to the currently used anti-fibrinolytic, epsilon aminocaproic acid (EACA).