Abstract: Twenty-four patients with prior myocardial infarction were studied who underwent thallium 201 stress-redistribution-reinjection positron emission tomography （PET）. All patients underwent thallium imaging 10min. 4h. 5h. 24h. and 72h after stress. In a total of 127 tomographic myoardial segments with definite post-stress thallium 201 perfusion defects, there were 57 segments （44.9％） to be perfused in 4h imaging. 68 segments （53.3％） in 5h, 55 （43.3％） in 24h and 76 （59.8％） in 72h imaging. When the criterion of late reversibility was defined as ≥1 segments with 4h nonreversible defects demonstrating late reversibility, it was presented in 13 （54.3％） of the 24 patients. In these 13 patients, there were only 1 segment late reversible in 4 patients （30.8％）, 2 segments in 5 （38.4）, ≥3 segmeuts in 4 patients （30.8%）. The Frequency of detected reversible defects increased from 29.29/0 in 4h imaging to 54.0％ in 72h imaging, P＜0.001. Our findings suggest that the reinjection late thallium imaging by PET could improve the rate of thallium reperfusion in the ischemic region and the differentiation of viable from infarcted myocardium. The reinjection late thalliun imaging was more sensitive than 4h delayed image in detecting hibernating myocardium.