Background: Therapeutic efficacy of combined platelet GP GP IIb/IIIa receptor blocker with low molecular weight heparin (LMWH) is not known in patients with acute coronary syndromes (ACS). The purpose of this study is to determine long-term clinical outcomes of abciximab in combined with LMWH, dalteparin in the high-risk percutaneous coronary intervention (PCI) patients with ACS. Methods: A total of 144 high-risk PCI patients with ACS was divided into two groups: UFH (group I: 70 patients, 58.9짹10.5 years), and daltaparin (group II: 74 patients, 60.0짹9.7 years). MACE (death, myocardial infarction, target lesion revascularization) during hospitalization and at 4 years after PCI was examintaed. Results: Baseline clinical characteristics, inflammatory marker, echocardiography parameter, baseline angiographic characteristics were not different between the two groups. ASTEMI was 81% and thrombotic total occlusion lesion was 62% in both group. Procedural success was achieved in 91.4% in group I and 90.5% in group II. Any bleeding and hemorrhagic event were not different between the two groups. No significant intracranial bleeding was observed in both groups. In-hospital MACE was 7 (10.0%) in group I and 4 (5.4%) in group II (p=0.23). Four-year clinical follow-up was performed in 97% patients. In MACE at 4 years after PCI, death occurred in 6 (8.6%) of patients in the group I and in 7 (9.5%) in the group II (p=0.54). Myocardial infarction occurred in 4 (5.7%) and 4 (5.4%) (p=0.60), repeat revascularization in 23 (32.9%) and 16 (2.6%) (p=0.13) and CABG in 3 (4.1%) and 1 (1.4%). Overall MACE occurred in 33 (47.1%) in group I and 26 (35.1%) in group II (p=0.09). Conclusions: Long-term clinical outcome with dalteparin combined with abciximab is comparable with that of UFH plus abciximab in high-risk PCI patients with ACS.