714 cases of Fallot's tetralogy have been encountered over the last thirty years. A closed heart operation was undertaken in 472 patients. The mean age at operation was 5,1 years. In 87% of cases, a Blalock-Taussig anastomosis was carried out. The operative mortality was of the order of 3%. The operative risk was almost three times as large before the age of two years as after. The patients benefit by a demonstrable improvement of function after this operation, but it does not protect them from the complications of the condition (cervica abscess, Osler's disease, cerebro-vascular accidents) or from death. Open heart surgery was carried out in 403 patients. 161 as a primary procedure, and 242 after an initial palliative operation. The mean age at operation was 13.3 years. The operative mortality was 15%. The functional improvement was striking, and the patients appeared to be protected from the usual sequelae of the condition. On the other hand they cannot always be considered as cured: 16 died some time after the operation; 37% had pulmonary incompetence; 15% had a residual BSD; 8% had a block of both bundles, and 3% had a definitive atrio-ventricular block.