We evaluated the time course of QT intervals and the amplitude of T waves, and their relationship to subsequent left ventricular regional wall motions in 88 patients with successfully reperfused acute myocardial infarction (MI). The QTc intervals and the amplitude of inverted T waves of lead V<sub>3</sub> in patients with anterior MI and of lead III in patients with inferior MI were measured for 1 month after MI. Patients were classified as having severe T wave inversion or mild T wave inversion within 3 days of MI, based on a measurement of 0.5 mV in the anterior MI cases and 0.3 mV in the inferior MI cases. Chronic-phase left ventriculography was performed 5 months later, and hypokinesis of the infarct site was measured using the centerline method. The T waves inverted after reperfusion in 86 patients (98%). The inverted T waves deepened twice, with the first negative peak about 48 h and the second negative peak about 18 days after MI. QTc intervals became prolonged as the T waves deepened. The extent of hypokinesis in the chronic phase correlated with the amplitude of inverted T waves and QTc intervals when the T waves were deepest. The group with severe T wave inversion had less extensive hypokinesis, a lower maximum serum creatine kinase level and a shorter time to reperfusion from the onset of symptoms than the group with mild inversion. We conclude that the degree of T wave inversion 48 h after MI is predictive of abnormalities in left ventricular regional wall motions in the chronic phase. A deep inverted T wave in the acute phase of MI indicates an abundantly stunned myocardium.