The late results of 146 patients with transposition of the great arteries (simple: 119, complex: 27) surviving to physiological correction (Mustard: 33, Senning: 113) are analyzed. The mean age at operation was 27 months (1-120), and the mean follow-up was 78 months (6-187). The mean P wave voltage significantly decreased (from 0.3 mV preoperatively to 0.16 mV postoperatively). Frontal mean P wave axis varied from 63.9 degrees to 71.3 degrees. Mean heart rate were significantly lower than those for age-matched normal children. Previous atrioseptectomy had been performed in 36 patients and five of them had arrhythmias before operation. 78 (55%) out of the remaining 141 showed arrhythmias in the surface ECG: sinus node disfunction in 51, tachyarrhythmias in eight, atrioventricular block in eight and several association of arrhythmias in 11. Actuarial survival free of arrhythmias is 81% at the first year, 49% at 5 years and 22% at 15 years. The incidence of arrhythmias in the group of 92 patients with Holter monitoring was higher, with 73 cases having arrhythmias (79%): sinus node disfunction in 47, tachyarrhythmias in ten, atrioventricular block in four and associated in 12. Survival free of arrhythmias by both methods (ECG and Holter) shows a 78% at the first year, 28% at 5 years and 5.6% at 15 years. No significant correlation was found between the incidence of arrhythmias and the type of TGA (simple or complex) or the surgical technique (Mustard or Senning). Permanent pacemakers were implanted in seven to a mean follow-up of 7 years. Five patients were reoperated to a mean follow-up of 46 months. There were 7 late deaths to a mean follow-up of 13 months, four of them being sudden. The actuarial survival rate for the whole group was 93.5% at 15 years. No significant correlation was found between the late mortality and the type of TGA or operation. There was also no correlation with the incidence of arrhythmias. Residual lesions were found in 46 patients, hemodynamically significant in ten. Functional status was class I (NYHA) in 123, and class II in 16. There was correlation between the functional class and the residual lesions.