The Wolff-Parkinson-White syndrome is caused by a congenital accessory connection between the atrium and ventricle. We describe a case of symptomatic Wolff-Parkinson-White syndrome that arose after a Björk modification of the Fontan operation. Invasive electrophysiologic and intraoperative mapping indicated that the surgically created atrioventricular connection was functioning as an accessory pathway. Surgical dissection and cryoablation abolished the symptoms and the preexcitation.