Background: We investigated the aerobic capacity of 168 adult patients who had undergone successful surgical repair of tetralogy of Fallot at the University of Toronto Congenital Cardiac Centre for Adults. Methods: We compared values of peak uptake of oxygen, peak heart rate, forced vital capacity, and forced expiratory volume in 1 second to predicted values for their age groups. Results: The patients who had undergone surgical repair of tetralogy of Fallot demonstrated an overall diminished peak uptake of oxygen, at 51%, and peak heart rate, at 79%, compared to predicted values. No difference in peak aerobic capacity was found according to the initial surgical strategy of palliation or repair. Conclusions: Adult patients who have undergone surgical repair of tetralogy of Fallot have lower peak uptake of oxygen, and peak heart rate, compared to predicted values. The reduction in the peak heart rate may affect their exercise capacity. The peak uptake of oxygen also decreased with increasing age at the time of testing, and the age at surgical repair.