A 38 year old man with arrhythmogenic right ventricular dysplasia underwent electrophysiologic study with extensive endocardial mapping of the right ventricle. During sinus rhythm, markedly reduced amplitude with or without prolonged duration was noted in multiple electrograms of the right ventricle. Delayed activation of the right ventricular outflow tract electrogram was present. Two clinical types of ventricular tachycardia with a left bundle branch block configuration and either an inferior or a superior axis were induced by ventricular stimulation. Endocardial activation sequence during the tachycardias suggested that the tachycardia with an inferior axis originated near the infundibulum, while that with a superior axis originated near the midinferior area of the right ventricle. Both areas have been previously shown to be frequently impaired in right ventricular dysplasia.