SummaryConcern about long-term complications after intraatrial repair of complete transposition has been used as an argument in favor of "anatomic" repair by the arterial switch operation. Late arrhythmias, including loss of sinus rhythm and the development of supraventricular tachycardias, particularly atrial flutter, are widely reported after intraatrial repair. Despite modifications of technique, the electrophysiologic substrate for arrhythmia results from the extensive atrial surgery required. Arrhythmias occur, even in the "modern surgical era" after both Mustard and Senning operations, are progressive, and appear to be inevitable. The circulation after an intraatrial repair is more vulnerable to the effects of excessive tachycardia, and this may place the patient at risk from sudden cardiac death. Current attempts at individual stratification of risk are disappointing using even aggressive electrophysiologic approaches, and a combined assessment involving hemodynamics is likely to be necessary. The electrophysiologic and arrhythmic consequences of the arterial switch operation have been less extensively researched but, as might be expected, are quite different from those seen after intraatrial repair. The atrial activation sequence is relatively undisturbed, and sinus nodal dysfunction and supraventricular arrhythmia are uncommon. Ventricular extrasystoles are the arrhythmia most consistently found during the short follow-up currently available. In the longer term, myocardial ischemia, hemodynamic disturbances and autonomic imbalance may predispose to late arrhythmia. Current evidence would suggest that the lack of clinically significant arrhythmia and the restoration of the left ventricle to the systemic circulation are significant advantages of the arterial switch operation over intraatrial repair procedures.