Tl201 MPS and MGCBS were performed on patients with myocardial infarction in the acute phase and the results were evaluated using a scoring system. The findings obtained in this study can be summarized as follows. There was a significant difference in RNEF between Killip class I and III. Significantly high correlation was noted between RWM score and RNEF. In cases of low RNEF (less than 35%) with poor RWM (less than 7), the incidence of complications, especially malignant PVC (47%, P less than 0.01) was markedly high. There was no obvious correlation between Tl201 MPS and complications. However, adding low RNEF (35% or less) to poor Tl scores (-22 or less) malignant PVC was noted with high frequency. Tl scores on admission were not related to the number of coronary arteries involved. For patients with good Tl score and low RNEF on admission (suspected of having severe ischemia), EF did not necessarily showed a tendency toward improvement. Patients with single-, tow- or three-vessel disease showed no difference in improvement of EF at discharge. There was no marked difference in Tl score on admission among three groups of single lesion of left anterior descending artery; patients with total occlusion without collateral circulation, patients with collateral circulation and patients with recanalization.