Most adolescents and young adults born with complete transposition of the great arteries (TGA) and alive today are survivors of the Mustard operation. This study reports on the serial, long-term (from 10 to > 20 years) follow-up of 85 patients who underwent this operation between 1971 and 1981. Of these, 63 had simple and 22 complex TGA. The age at surgery ranged from 2 days to 17 years. The early mortality rate was 10.5% and the late mortality 9.2%. The actuarial survival rate after 15 years was 86% for simple and 64% for complex TGA. Event-free survival after 15 years was 77% for simple and 46% for complex TGA. Yearly review of electrocardiograms and, less frequently, of Holter tracings disclosed a lower mean resting heart rate and decrease over time in sinus rhythm and an increase in active arrhythmias. Fifty-two percent had resting sinus rhythm and 17% had active arrhythmias at 16 to 20 years of follow-up. Exercise stress testing in 21 patients revealed resumption of sinus rhythm during exercise but significant diminution of endurance time and peak heart rate response. Seven of the survivors (9.2%) required reoperation. Of these, 4 had severe tricuspid regurgitation following patch closure of ventricular septal defect. This study shows gratifying long-term and event-free survival for the majority of patients who underwent surgery by this venous switch procedure.