Certain surgical interventions can perturb the hemostatic system significantly, making the patient prone to intraoperative and postoperative thrombus formation. The consequences of unabated thrombus formation can be devastating. The risk of developing deep vein thrombosis (DVT) after certain surgical procedures can be as high as 40% to 80%, while the incidence of fatal pulmonary embolism is 1% to 5%. 11 , 49 Antithrombotic therapy is usually instituted perioperatively, and has significant impact on the choice of anesthetic technique. 1 , 26 Anticoagulation is an imperative part of vascular reconstructive procedures, as iatrogenic cessation of blood flow and exposure of thrombogenic subepithelial surfaces can act as a nidus for arterial thrombus formation. Furthermore, cardiopulmonary bypass (CPB) procedures with extracorporeal circulation cannot be possible without intraoperative anticoagulation. Intraoperatively, unfractionated heparin (UH) is used most commonly to inhibit coagulation. Although it will likely continue to be used extensively in the near future, newer agents are on the horizon. These agents may be used in clinical situations where heparin is either contraindicated, or where more predictable responses with less side effects are needed. Because of their wide clinical use, it is imperative to be familiar with heparin and the newer anticoagulant agents. Furthermore, surgical interventions, anesthetics, and some commonly used medications affect coagulation. These effects on the hemostatic system will be reviewed, followed by a discussion of antithrombotics, perioperative monitoring, and clinical management. Intraoperative use of thrombolytics and anesthetic implications of anticoagulation will be discussed.