Dextro-Transposition of Great Arteries (d-TGA) was repaired by Mustard's operation in 69 patients during a 10 year period (1973-1982) in our institution. Ages at the time of surgery ranged from 3 months to 18 years, with a median age of 18 months. Factors that most affected mortality and morbidity were associated cardiac defect, the year of the operation and the age of the patient. Of the 69 patients, 26 (38%) had complex d-TGA. Early post-operative mortality was 2.38% for patients with simple transposition and 22% for the complex group. All early deaths occurred in the early part of series. Ten consecutive cases with complex transpositions in the late part of the series have done well. There were 5 late deaths--4 from the early series and these had complex transposition. Postoperative non-fatal complications included arrhythmia which occurred in 6 patients (9%). The rhythm abnormality was temporary in 2 and permanent pacing was required in 2 other patients (2.9%). There were 3 cases of late caval obstruction and 4 cases of late pulmonary venous obstruction--six of these seven patients were less then 12 months of age. Postoperative renal failure occurred in patients in the early series but was not seen in the late series. Three children developed postoperative pulmonary edema due to large bronchial collateral arteries and underwent successful collateral vessel ligation subsequent to the Mustard operation. Two patients have demonstrated late tricuspid regurgitation, are presently in heart failure and may need valve replacement.(ABSTRACT TRUNCATED AT 250 WORDS)