Background: The efficacy of the hemostasis of prophylactic aprotinin after cardiac valve replacement was evaluated from January 1994 to December 1996 at Pusan National University Hospital. Material and Method: In a randomized study, 20 patients received aprotinin(2${ imes}$106 KIU as a loading dose for 30 minutes after anesthesia, 1${ imes}$106 KIU for priming and 5${ imes}$105 KIU/hr as a maintenance dose from the completion of loading dose till skin closure) and another 20 untreated patients served as controls. Result: Aprotinin produced a significant reduction in postoperative blood loss compared with controls and significantly decreased total exposure to allogenic blood products compared with the control group(p<0.05). Conclusion: We conclude that aprotinin effectively reduces postoperative blood loss and trasfusion in patient undergoing cardiac valve replacement.