Intravenous unfractionated heparin (UFH) has been shown to be an effective therapy in reducing the risk of death or myocardial infarction in patients with unstable angina. Low molecular weight heparins demonstrate improved pharmacologic and pharmacokinetic properties relative to standard heparin, and these advantages have been translated into similar or even greater clinical efficacy in several large-scale clinical trials evaluating their use. The simple mode of administration and lack of dependency on anticoagulation monitoring make low-molecular-weight heparins an extremely attractive option in the treatment of patients with acute ischemic coronary syndromes presenting without persistent ST-segment elevation.