After surgery for complex congenital heart disease, clinically important atrial tachyarrhythmias have a higher than normal incidence if sufficiently large regions of conduction block occur within the atria, especially in the presence of hemodynamic alterations. Sinus bradycardia may result from direct damage to sinus node and its blood supply. Historical data have identified patients who have undergone the Mustard or Senning operations for dextrotransposition of the great vessels and the Fontan operation in cases of functional single ventricle as being at great risk for atrial tachyarrhythmias. These arrhythmias are especially poorly tolerated when there are co-existing hemodynamic alterations and are an important source of morbidity and mortality. Until recently, treatment strategies have been limited to antiarrhythmic drugs, bradycardia pacing, and--in suitable patients--antitachycardia pacing, often in combination. Amiodarone has been the most efficacious drug, but has only been of moderate value because of extracardiac side effects. Radiofrequency ablation of the atrial regions critical to reentrant circuits, which was discovered to be of value in patients with atrial flutter and a normal heart is being applied to this diverse group of patients. Early results are promising, but the Fontan operation patients are especially challenging because of early recurrences of apparently new reentrant circuits. Progress in this area will likely come from newer surgical techniques that prevent the milieu for atrial reentry and from multidimensional mapping systems for our current patients.