A 42-year-old man was admitted to our hospital because of acute heart failure. He had suffered inferior myocardial infarction 6 years ago. At that time, electrocardiogram (ECG) showed prominent Q waves in inferior leads (Fig.1A), and inferior wall of left ventricle was hypokinetic. He had interrupted regular medication 4 years ago. On admission, left ventricle was diffusely hypokinetic with 20% of ejection fraction, and there were no prominent inferior Q waves in ECG. (Fig.2) Through resuming previous medications, he was discharged uneventfully. One year later, echocardiogram revealed restored LVEF, and it is interestingly to note that ECG showed prominent inferior Q waves as previously exhibited. (Fig.1B) Q waves following myocardial infarction are the sign of loss of electromotive forces due to myocardial necrosis. The appearance of Q waves is believed to depend on the size and extent of infarction. The temporally disappearance of Q waves in this case suggested that the development of Q wave depends not only on regional loss of electromotive potentials in the infarct area but also on preserved electromotive potentials from the opposite ventricular wall.