Objective: To compare the effects of aprotinin on blood product use and postoperative complications in patients undergoing thoracic aortic surgery requiring deep hypothermic circulatory arrest.Design: A retrospective study.Setting: A university hospital.Participants: Nineteen patients who underwent elective or urgent thoracic aortic surgery.Interventions: None.Measurements and Main Results:The total number of units of packed red blood cells, fresh frozen plasma, and platelets was significantly less in the group that received aprotinin (p = 0.01, 0.04, and 0.01), The intraoperative transfusion of packed red blood cells and platelets, collection and retransfusion of cell saver, and postoperative transfusion of fresh frozen plasma were also significantly less in the aprotinin group (p = 0.01, 0.02, 0.01, and 0.05). No patient in either group sustained renal dysfunction or a myocardial infarction. Two patients who had not received aprotinin suffered from chronic postoperative seizures, and one patient who had received aprotinin sustained a perioperative stroke.Conclusions: Low-dose aprotinin administration significantly decreases blood product transfusion requirements in the setting of thoracic aortic surgery requiring deep hypothermic circulatory arrest, and it does not appear to be associated with renal or myocardial dysfunction. Copyright (C) 2000 by W.B. Saunders Company.