The problem of altered hemostasis remains a major challenge during thoracic aortic surgery. Bleeding is associated with a marked increase in morbidity and mortality. The hemostatic derangements are caused by multiple interrelated factors including interference with the vascular integrity, extensive surgical dissection, transient need for complete inhibition of the normal coagulation process, large blood products and fluid requirements, hemodilution, hypothermia, extensive ischemia and reperfusion, activation of systemic inflammatory responses, interference with fibrinolysis, and the use of extracorporeal circulation systems. Acquired coagulopathy must be specifically diagnosed and treated. Platelet deficiencies, both qualitative and quantitative, are the most predictable and consistent disturbance in the hemostatic function and the most common cause of intraoperative and postoperative bleeding. Precise surgical technique is essential to prevent blood loss. Topical agents should not be used for and cannot correct imperfections in surgical technique. Nonspecific measurements that are useful to decrease intraoperative blood loss include strict control of blood pressure and hemodynamic status, the induction of mild controlled hypotension, and the reversal of hypothermia. Rewarming may produce clear procoagulant effects by improving the efficacy of platelets and clotting factors. Platelet dysfunction can be reduced by several pharmacological interventions including acid aminocaproic, desmopressin and aprotinin; however, efficacy and safety are still being established. The most important factorS regarding safety in thoracic aortic surgery are a secure suture line and the experience of the surgical and anesthesiology teams.