Idiopathic ventricular tachycardia is rare, especially in infants. We report here on an 8month-old female infant who presented with tachycardia with a heart rate of 186 beats/min. An electrocardiogram showed a right bundle branch block pattern, a QRS duration of 80 msec, a superior QRS axis, atrioventricular dissociation, and occasional fusion and capture beats. Suspected ventricular tachycardia was treated with lidocaine, propranolol and amiodarone, but in vain. The tachycardia was terminated and well controlled with the use of verapamil. According to an electrocardiogram and her clinical response, verapamil-sensitive idiopathic ventricular tachycardia was diagnosed with the arrhythmic origin in the left posterior fascicle.