A 16 year old female with tricuspid atresia had undergone a Fontan operation at four years of age. Two years later she first presented with a narrow complex tachycardia which could only be partially controlled on flecainide in high doses. On electrophysiological study, the tachycardia was found to be due to atrioventricular re-entry within the surgical right atrial to right ventricular outflow tract anastomosis. Radiofrequency ablation at this site abolished the arrhythmia and she is now symptom-free on no medication.