A dual chamber permanent pacemaker was implanted into an asymptomatic man with complete (third degree) heart block because of the risk of asystole. The ventricular lead was thought to have been attached to the right ventricular septum; however, it inadvertently passed through a patent foramen ovale into the left ventricle. Although the postprocedure ECG showed right bundle branch block this was thought to be due to the presumed septal positioning of the pacing lead. Lead misplacement was not detected on posterioanterior chest X-ray but was clearly demonstrated by transthoracic echocardiography, and subsequently on lateral chest X-ray. The lead was successfully removed and repositioned correctly at the next available opportunity without complication or sequelae.