Standard 12-lead ECGs were evaluated in 17 children with myocardial infarction and 78 children without myocardial infarction after Kawasaki disease; sensitivity and specificity of the ECG infarction criteria were determined. The presence or absence of myocardial infarction was determined from either clinical examination results (coronary anglography, ventriculography, and thallium-201 myocardial imaging) or autopsy findings. Of seven patients with inferior infarction, abnormally deep Q waves in lead II, III, or aV F were observed in six, but the duration was greater than 0.04 second in only one (14%). The sensitivity and specificity of inferior infarction criteria based on Q wave amplitude were 86% and 97%, respectively. Of eight patients with anterior infarction, seven (88%) had abnormally deep and wide (≧0.04 second) Q waves in anterior chest leads. The sensitivity and specificity of the infarction criteria based on the amplitude and duration of the Q wave were 75% and 99%, respectively. Of seven patients with lateral infarction, Q waves were observed in lead I, aV L, or both in four patients, and in all of these patients Q waves were wider than 0.04 second. In two patients with both inferior and anterior infarction, Q waves were observed only in leads II, III, and aV F; in only one patient were the Q waves wider than 0.04 second. Thus deep Q waves in lead II, III, or aV L that are not wider than 0.04 second may indicate inferior infarction in children. Q waves in lead I, aV L, and chest leads associated with anterolateral infarction are in most instances deep and wide.