Background: Previous several trials revealded efficacy and safety of low molecular weight heparin(LMWH) compared to unfractionated heparin(UF) in patients with Non-ST-Segment Elevation Acute Coronary Syndrome(NSTE ACS). But whether LMWH is superior to UF in NSTE ACS patients undergoing percutaneous coronary intervenstion(PCI) under Early invasive strategy remained unclear. This study was aimed to evaluate the outcomes of patients with NSTE���ACS who underwent PCI for Early Invasive Strategy within 48 hour treated with LMWH vs UFH. Methods: A total of 4819 NSTE ACS���patients who were enrolled Korea Acute Myocardial Infarction Registry(KAMIR) from November 2005 to January 2008. Among those patients, only patients who underwent PCI treated with Invasive strategy within 48 hours after admission were selected. Finally 816 patients were divided into two groups. (Group I; n=588, UFH, group II; n=228, LMWH). Clinical outcomes were assessed at in-hospital and 1 year. Results: Group I was similar to group II in terms of demographics, clinical characteristics. Door to balloon time of group II was significantly faster than group I(1088.28짹808.08min vs. 633.12짹705.11min, p=0.001). But PCI success rate was not different between two groups(96.9% vs. 95.8%, p=0.507). Group II more medicated cilostazole than group I(34.7% vs. 21.1%, p=0.001). Major bleeding complications were not different between two groups. In-hospital death rate was lower in Group II than Group I(12.4% vs. 1.3%, p=0.423). 1 year death rate was slightly lower in Group II compared with Group I(6.7% vs. 3.1%, p=0.116). Consequently, in-hospital and 1 year death tend to lower in group II than group I but statistically not significant. Conclusions: There were no differences in major bleeding complications and in the rate of cardiovascular death during clinical follow-up period between two groups. Further study using KorMI(Korea Working Group on Myocardial Infarction) data is being watched with identify this conclusion.