BACKGROUND: It is known that QT dispersion represents asynchronous repolarization of ventricle which is related to ventricular fibrillation. The incidence of ventricular arrhythmia is increased after acute myocardial infarction. So this study compared QT dispersion and other repolarization indexes for detection of asynchronous repolarization in acute myocardial infarction. We also investigated which portion of repolarization is the key portion of the asynchrony. METHODS: In 37 acute myocardial infarction patients and 38 angina patients dispersion of QT, JT, JTpeak and QTpeak were measured. We also measured maximum adjacent dispersion of same parameters in precordial leads. In 20 survived patients and 17 dead patients after acute myocardial infarction were also compared. We also investigated correlation of PVC's on Holter monitoring with these repolarization parameters. RESULTS: 1) All ventricular repolarization indexes(QT, QTc, JT, JTpeak, QT peak and TpeakTend dispersion) were significantly increased in acute myocardial infarction group than compared with those of angina group(p<0.05). 2) Maximal precordial dispersion(QT, QTc, JT, JTpeak and QTpeak) were also significantly increased in acute myocardial infarction group than angina group(p<0.05). 3) Dead patient group after myocardial infarction showed significantly increased QTc and TpeskTend dispersion compared with those of survived patient group(p<0.05). 4) Multivariate linear correlation showed that TpeakTend dispersion and JT dispersion was correlated with QT dispersion. CONCLUSIONS: There were asynchronous myocardial repolarization changes in acute myocardial infarction. Our study demonstrated that T wave change was major determinant of dispersion of myocardial repolarization.