The diagnosis of the location and size of old myocardial infarction was made by the map and various indices obtained from the map were correlated with coronary arteriography, left ventriculography, and 201Tl myocardial scintigraphy. Diseased coronary arteries were presumed from Q30, Q40 area and/or peak voltage map and left ventricular wall motion was estimated from subtraction map. There were significant correlations between ejection fraction and sigma R in anterolateral MI (r = 0.51, p less than 0.001) and between ejection fraction and nQ30 in anterolateral (r = -0.47, p less than 0.001) and inferoposterior (r = -0.63, p less than 0.01) MI. Negative correlation was observed between myocardial uptake ratio (MUR) and nQ30 (r = -0.69, p less than 0.001) and positive correlation between MUR and sigma R (r = 0.50 p less than 0.01) in anterolateral MI. Those cases which could not be diagnosed by either ECG or 201Tl scintigraphy were correctly diagnosed by the map and it proved to have an excellent diagnostic accuracy for myocardial infarction.