Coronary artery diseases continue to be the most common causes of mortality and morbidity in the industrialized world, especially in the setting of acute myocardial infarction. Anticoagulation during primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI) has traditionally been supported by anticoagulant unfractionated heparin (UFH). Recently, alternative anticoagulants such as low molecular weight heparin (LMWH) were included in the management of STEMI. The aim of the present review is to compare efficacy and safety outcomes among patients receiving low molecular weight heparins (LMWH) or unfractionated heparin (UFH) while undergoing PCI for STEMI.