Venous thromboembolism has been increasingly recognized as a significant contributor to patient morbidity and mortality, and there has been rapid growth in the application of interventional techniques to the management of venous thrombotic disorders. For the physician managing a patient with a venous thrombosis, an excellent understanding of the mechanisms of disease, thrombosis physiology, pathophysiology of clotting disorders, data to support the application of different pharmacologic interventions, and risks and benefits of different therapies is critical to success. This chapter provides a thorough overview of the science and pharmacologic management of thrombosis, as well as details of patient evaluation, epidemiology, and expected outcomes of intervention.