- The introduction of low-molecular-weight heparins (LMWHs) has contributed to major improvements in the management of venous thromboembolism (VTE). The LMWHs have been shown to be as effective as, and safer than, unfractionated heparin (UFH) in the prevention and treatment of VTE, and their use is included as a grade 1A recommendation in the Sixth American College of Chest Physicians Guidelines. Important practical disadvantages of treatment with UFH are the need for extended hospital stays and frequent monitoring of coagulation levels. In comparison, LMWHs offer convenient and cost-effective prophylaxis and treatment of VTE on an outpatient basis. The LMWHs have also had a major impact on the management of arterial thromboembolism. In patients with acute coronary syndromes (unstable angina and non-ST-segment elevation myocardial infarction), enoxaparin has demonstrated sustained clinical improvements in major ischemic outcomes compared with UFH. Antiplatelet agents have also contributed significantly to the development of effective antithrombotic therapy. Aspirin is the best known antiplatelet agent and has heretofore been the mainstay of antiplatelet therapy in unstable angina. New data indicate that combination therapy with aspirin and a novel thienopyridine, clopidogrel, may further improve outcomes in this indication.