Background: Several studies have shown that nicorandil, a hybrid ATP-dependent potassium channel opener and nitrate compound, have a cardioprotective effects in ischemic heart disease. We assessed whether the intracoronary administration of nicorandil followed by oral administration exerts beneficial effect on cardioprotecton and clinical outcomes in patients with PCI for ACS. Method: We randomly divided 42 patients, except 7 ones who had a PCI related complication, into two groups, nicorandil(n=23, male :16, mean ages : 61.9짹10.1 years) and control group(n=19, male : 12, mean ages : 60.1짹11.1 years). In the nicornadil group, we injected 2mg of intracoronary nicorandil just before PCI and followed administration of oral nicorandil(15mg/d). Serum levels of CK-MB were measured 6 and 18 hours after PCI and angiographic results and clinical events were evaluated. Results: All patients in both groups received successful coronary PCI. Incidence of CK-MB elevation(above upper normal limit) at 6 hours were less common in nicorandil(0/23) compared to control group(3/16)(p=0.048). But there was no difference between two groups in incidence of CK-MB elevation at 18 hours(15.8% vs 18.7%, p=0.846). Slow/no flow was also less common in nicorandil group(0% vs 18.8%, p=0.048) The incidence of MACE of In-hopital and during follow-up period were not different between both groups. Conclusion: Pretreatment with intracoronary administration of nicorandil suppressed CK-MB release as well as improved coronary flow after PCI in patient with ACS, suggesting cardioprotective effects of nicorandil.