Background : The TIMI myocardial perfusion grade (TMPG) reflects myocardial perfusion and is associated with long term clinical outcomes. This study was to compare the TMPG as the parameter of reperfusion with the prediction of myocardial viability as determined by fluorine-18 deoxyglucose positron emission tomography (FGD-PET). Methods : We collected clinical, biochemical and angiographic information in 44 consecutive patients ( 37 men and 7 women; age 56 짹 11 years) who underwent primary PCI for ST segment elevation myocardial infraction (STEMI) from May, 2004. After PCI, we assessed coronary flow reserve (CFR), diastolic deceleration time (DDT) by intracoronary Doppler wire. All patients underwent FDG-PET scan on the 7th day after primary PCI. The patients were divided into 3 groups according to the TMPG (TMPG 0/1: n=18, TMPG 2: n=14, TMPG 3: n=12). Results : There were no significant differences in reperfusion time (onset to balloon time) and cardiac enzyme among the groups. The patients with the TMPG 3 had the highest CFR, DDT and the most favorable FDG uptake rate (Table). We found that there was a significant difference in the incidence of the patients with viable myocardium among the groups (Table). Conclusions : The angiographic TMPG might be clinically useful for assessment of myocardial viability in patients with STEMI during primary PCI.