Low-molecular-weight heparins have several important advantages over unfractionated heparin (UFH). Due to a longer plasma half life together with high bioavailability and a linear dose-response relationship, the drugs can be safely and effectively administered in the hospital or ambulatory settings without the need to monitor the anticoagulant effect. Enoxaparin (Lovenox), Aventis Pharma) is a low-molecular-weight heparin which has been studied in a variety of clinical situations. In general surgery the efficacy of enoxaparin to prevent venous thromboembolism is similar to UFH but the tolerability is better. In patients undergoing cancer, orthopedic or vascular surgery the efficacy of enoxaparin is significantly higher with similar rates of bleeding complications. The database for enoxaparin in nonsurgical patients is smaller compared with surgical groups. There is evidence that the efficacy of enoxaparin may be superior to UFH in patients with severe cardiac disease. Efficacy and safety of UFH and enoxaparin are similar for the treatment of deep vein thrombosis. However, enoxaparin can be safely administered by the patients at home which is not possible with UFH. In patients with acute coronary syndromes, enoxaparin has been shown to reduce the rate of deaths and serious cardiac events in comparison with UFH. Furthermore, exonaparin treatment has been shown to be cost-effective, and therefore is the therapy of choice in this setting. In addition, enoxaparin has been shown to be a safe and effective alternative to the combination of UFH and phenprocoumone therapy in patients undergoing electrical cardioversion for atrial fibrillation.