Platelet aggregation, and activation of coagulation cascade are the key events in the development of acute coronary syndromes (ACS). Patients with this syndrome are at high risk of adverse events, such as death and myocardial infarction (MI). Optimized medical treatment for the non-ST segment elevation ACSs should consist of a combined antithrombotic / anti-anginal regimen. Standard anti-thrombotic treatment is currently unfractionated heparin (UH) and aspirin, and in high-risk patients glycoprotein IIb / IIIa inhibitors. UH has been shown to reduce the risk of death or myocardial infarction in aspirin-treated patients with ACSs, but it has a number of limitations, such as need for regular monitoring and the risk of hemorrhage and thrombocytopenia. Compared to UH, the low molecular weight heparins (LMWH) possess several important theoretical advantages for the treatment of patients with ACSs, including less non-specific binding, resistance to inactivation by platelet factor-4, more reliable anticoagulation effects, and greater factor anti-Xa activity. Recently published trials strongly support the use of LMWHs in the treatment of ACSs. These agents provide an alternative to UH that is at least as effective. The available evidence favours the use of these agents in acute cardiac care. This article explores the recent clinical data on the use of LMWHs in acute cardiac care, and looks critically at the differences between traditional therapies. Recommendations regarding the use of anti-thrombotic agents in patients with ACSs are also discussed.