Seventeen patients with a previous myocardial infarction were studied during pacing to characterize the clinical correlates of ST elevation, to analyze the relation between ST elevation and negative T-wave normalization and to investigate the mechanism of these electrocardiographic changes. Myocardial ischemia was evaluated by measurement of blood lactate, and wall motion was analyzed using cardiokymographs concurrently and serially. Results show that ST elevation and negative T-wave normalization were most marked in leads containing abnormal Q waves, that ST elevation greater than or equal to 1 mm during pacing was associated with a significant increase in left ventricular end-diastolic pressure and deterioration of left ventricular wall motion and that the magnitude of ST elevation and negative T-wave normalization was significantly correlated, but the latter appeared earlier and more markedly. In addition, there was no significant correlation between the extent of either ST elevation or negative T-wave normalization and myocardial lactate production. Thus, ST elevation and negative T-wave normalization are caused by abnormal left ventricular wall motion rather than myocardial ischemia. Negative T-wave normalization is a more sensitive marker of abnormal wall motion than ST elevation in patients with a previous myocardial infarction.