Background: It has been reported that nicorandil have a cardioprotective effect in experimental ischemia-reperfusion models. In the present study, we investigated the cardioprotective effect of nicorandil as an adjunct to reperfusion therapy in patients with acute myocardial infarction (AMI). Methods and Results: One hundred consecutive patients with AMI were randomized into 2 groups: (1) Group I: nicorandil was given at 4 mg intravenously before reperfusion, followed by continuous infusion at 4mg/h for 48 h; (2) Group II: Isosorbide dinitrate (ISDN) was given by continuous infusion for 46hr (4 – 8 mg/hr). Echocardiography was performed immediately after reperfusion and 1 month later. Successful PCI was performed in 83 patients (Group I = 43, 57 짹 12 years, Group II = 40, 57짹 9 years). There were no significant differences in clinical and angiographic characteristics between two groups. After 1 month, change of regional wall motion and left ventricular (LV) ejection fraction were not different between two groups. However, LV end-diastolic volume was significantly decreased in nicorandil group (��LVEDV; -2.9 짹3.8 vs. 6.3 짹 5.7 ml, p=0.001). LV filling pressure measured by E/e��� ratio was significantly improved in nicorandil group (��E/e���: -0.03 짹 2.47 vs. 1.96 짹 3.7, p=0.04) Conclusions: The early administration of nicorandil as an adjunct to reperfusion is useful for cardioprotection.