The purpose of the present study was to clarify the characteristic findings of electrocardiogram (ECG) in 11 patients with acute myocarditis. ST elevation without reciprocal ST depression was one of the conspicuous findings in the acute stage. Total QRS amplitudes at the acute stage were significantly decreased as compared to those before illness and during the convalescent stage. Abnormal Q waves were present in 7 patients and disappeared in a short period. The number of leads showing Q waves was inversely correlated to left ventricular (LV) ejection fraction (r = -0.87, p < 0.01). Conduction disturbances were present in 7 patients. Second degree and advanced AV block was transient while bundle branch block remained over months. Corticosteroid treatment was effective for patients who had edematous myocardial thickening and AV conduction disturbances. As the serial ECG findings in acute myocarditis are so characteristic, and this help to differentiate it from acute myocardial infarction (AMI).