Background: drug-eluting stents (DES) remarkably reduced the rate of in-stent restenosis and repeat revascularization, improving the clinical outcomes. However safety concerns ,including stent thrombosis, of DES is still remained especially in acute coronary syndrome(ACS). Recently new generation stent, Endeavor ResoluteTM stent with zotarolimus and biocompatible polymer, was developed. So we intended to demonstrate the efficacy and safety of it in the ACS setting, as compared with original EndeavorTM stent. Subjects and Methods : We included 196 patients who were presented as ACS. They were randomized into EndeavorTM(N=86) and Endeavor ResoluteTM(N=110) stent group at the time of percutanous coronary intervention(PCI). We planned to check the in-hospital events, including procedural complications, periprocedural elevation of cardiac markers (CK-MB and troponin) and bleeding, and clinical status at 1 and 3 month, and to take the coronary angiography at 9 month after index PCI. Results : Baseline clinical characteristics of subjects were not different between two groups. Two thirds of all subjects was ST elevation(24.4 in EndeavorTM group vs 30% in Endeavor ResoluteTM group) and non-ST elevation myocardial infarction(25.6 vs 24.5%). Lesion characteristics between two groups were not different; type B2/C lesion (62 vs 64%), multivessel disease (67.4 vs 61.8%). GP IIb/IIIa blocker was not used in most subjects (89.5 vs 87.3%). There were no difference in number(1.19짹0.43 vs 1.16짹0.46mm), size(3.2짹0.49 vs 3.15짹0.45mm), and length(22.39짹5.37 vs 23.09짹6.30mm) of stents used between two groups. There was no event in both in-hospital period and 1 month in both groups. At 3 month after PCI, the incidence of MACE was not different between two groups; death (0 vs 1), which was related to lung cancer, no myocardial infarction and repeat revascularization. Conclusion : During the short-term period (3 month), Endeavor ResoluteTM stent as well as EndeavorTM stent showed good clinical efficacy and safety in ACS patients. We expect that coronary angiography at 9 month may demonstrate the efficiency of Endeavor ResoluteTM stent in the setting of ACS.