Excessive bleeding during and after cardiac surgery is a serious complication. It exposes patients to the risk of allogeneic blood transfusion or other blood products and the risk of mediastinal re-exploration.Antifibrinolytic drugs like aprotinin and tranexamic acid are proven to reduce bleeding tendency and transfusion requirement in cardiac surgery. The efficacy of these drugs is proven, especially for the unspecific proteinase inhibitor aprotinin, however, there are concerns about the safety and the high costs of this drug. There are only limited head-to-head comparisons of these two drugs.