It is important to understand the prevalent need for anticoagulant and antithrombotic medications in the current era of cardiovascular medicine. Many new anticoagulants are currently undergoing human clinical trials to assess their efficacy and safety profile compared with the time-honored, standard agents. It is critical that anesthesiologists be familiar with the mechanisms of action, durations of effect, and potential side effects of currently used and new anticoagulant agents so they can participate in decision-making processes that involve the timing of surgery and the appropriateness of regional anesthesia for patients in whom these agents have been employed. It also is important to be familiar with the various mechanisms by which antiplatelet agents act to inhibit platelet function, because this understanding allows a rational approach to restoration of hemostatic competence where necessary. The ability to monitor the hemostatic defect induced by antiplatelet agents and the incorporation of such tests into therapy-directed algorithms ultimately will reduce bleeding complications and the occurrence of empiric transfusions.