A 3-year-old boy had chronic repetitive atrial tachycardia. The tachycardia could not be induced neither terminated with rapid atrial pacing nor atrial extrastimuli. Overdrive suppression and warm-up phenomenon were demonstrated. These electrophysiological features suggested atrial ectopic automaticity. Endocardial and epicardial mapping determined the origin of tachycardia at the left atrial appendage. The LA appendage was excised and the tachycardia was completely terminated. The patient is asymptomatic without medication and echocardiographic indices of left ventricular function returned to normal over 1 year follow-up period.