Acute coronary syndromes (ACS) represent a spectrum of diseases resulting from a disturbance in myocardial blood flow. The etiology of this disturbance stems from either partial or complete thrombotic occlusion of the culprit vessel. Appropriate antithrombotic therapy is crucial in limiting the progression of ACS. Conventional antithrombotic therapy in ACS has typically utilized unfractionated heparin (UFH). However, UFH has several limitations that may restrict its clinical usefulness. Direct antithrombin agents are currently not indicated for ACS and have the potential for problems including a narrow therapeutic window and bleeding. The low-molecular-weight heparins offer a convenient and attractive alternative, which, in the case of enoxaparin, have demonstrated superiority over UFH in two large randomized trials. Low-molecular-weight heparins (LMWH) represent an important therapeutic advance in the management of ACS and additional information is forthcoming that will better define the role of LMWH in ACS.