Introduction. According to the published guidelines for the management of acute coronary syndromes (ACS), treatment of acute ST-elevated myocardial infarction is based on rapid revascularization, either mechanical or pharmacological. Pharmacological revascularization consists of fibrinolytic therapy with antiplatelet and anticoagulant therapy. In regard to the anticoagulant therapy, low molecular weight heparins (LMWHs) are of special importance. LMWHs cause less complications (bleeding, thrombocytopenia, better bioviability) in comparison with unfractionated heparin (UFH). Some studies on use of LMWHs in ACS, show that LMWHs are equally efficient and safe as UFH, causing less complications (different types of hemorrhagic complications) (ESSENCE, TIMI 11B (enoxaparin), FRAXIS - fraxiparin), whereas some studies show better efficacy and safety of enoxaparin in therapy of acute ST-elevated myocardial infarction (ASSENT 3, ASSENT 3 PLUS, HART II, AMI-SK). Material and methods. Inclusion criteria: acute anterior myocardial infarction with ST-elevation, first myocardial infarction, no other structural heart defects, no signs of cardiogenic shock. Our study included 30 patients receiving fibrinolytic therapy with streptokinase, antiplatelet therapy and LMWH during 6 days, and 30 patients receiving UFH instead of LMWH. The follow-up period lasted for 6 months. Results. Significantly more patients receiving unfractionated heparin presented with major adverse cardiac events (73.3%) in regard to patients in the study group (44,2% nadroparin, 39.8% enoxaparin) (p=0.025). In the group receiving UFH, 6.7% patients had hemorrhagic complications, while none of patients receiving LMWHs. An equal number of patients died. Conclusion. Patients who were treated with LMWHs experienced less major adverse cardiac events and lower mortality. None suffered from hemorrhagic complications. .