Cardiac PET elicits an accurate relationship between myocardial blood flow (MBF) and tissue viability, which is evaluated by myocardial FDG uptake (MFU). To differentiate reversible tissue from necrotic tissue after the ischemic event, we from necrotic tissue after the ischemic event, we measured absolute MBF and MFU in patients with myocardial infarction. The MBF obtained by O-15 water and dynamic PET was accurately corrected by employing a tissue fraction (a) for the partial volume effect, including wall-motion effect. MFU was also corrected by using the tissue fraction. The subjects consisted of 5 patients with non-Q-wave infarction and 7 patients with Q-wave infarction. The regions of interest were selected from the infarcted area, each corresponding to regions with Q-wave or non-Q-wave. The MBFs in regions with Q wave (0.36 +/- 0.14 ml/min/g) were lower than those without Q wave (0.74 +/- 0.29 ml/min/g) (p less than 0.005). MFUs in regions without Q-wave (0.061 +/- 0.028) were higher than those with Q-wave (0.038 +/- 0.017) (p less than 0.05). The highest threshold of MBF in regions where Q-wave was detected was 0.55 ml/min/g. It is concluded that we will able to find the threshold of electrophysiological dysfunction in the infarcted region with this method.