Twenty-six patients requiring palliation for the tetralogy of Fallot were treated by balloon dilation. The mean age at dilation was 8.5 months (range 0.5−20.6) and the mean weight 6.7 kg (range 2.6−10.7). Successful dilation was achieved in 25 patients. The mean ratio of the balloon to the diameter of the pulmonary outflow tract was 1.6 (range 1.2−2.0). The aortic oxygen saturation increased from mean±SD of 80±12.4% before to 91±4.3% after dilation (p<0.05). The pulmonary arterial oxygen saturation rose from 64±10.7% to 80±7.7% (p<0.05). Transient hypotension and arterial desaturation were noted in 19 patients during inflation of the balloon. One patient had a cardiac arrest prior to dilation and died afterwards. Seven patients had cyanotic spells related to the procedure. Attempts to cross the pulmonary valve resulted in infundibular perforation by the guide wire in one patient. Of the 24 survivors who initially had successful dilation procedures, three have needed a Blalock-Taussig shunt. Palliation without a shunt was achieved in the remaining 21 patients. In 12 patients, repeat angiography, 2.5−20 months (mean 9.1) after dilation, showed an increase in the diameter of the outflow tract from 7.1±2.1 mm before to 9.5±2.0 mm after dilation (p<0.05). Diameters of the pulmonary arteries increased from 6.3±2.2 mm on the right and 6.8±1.9 mm on the left before to 9.2±2.2 mm and 9.3±2.5 mm respectively after dilation (p<0.05 for both branches). Surgical correction has been achieved in 22 patients, 21 of these 2−22 months after balloon dilation and the other patient 20 months after construction of a shunt. At operation, the leaflets of the pulmonary valve were noted to be torn in five patients. In 12 patients, there was extensive scarring of the infundibulum. Balloon dilation of the right ventricular outflow tract achieves adequate palliation and may result in an increase in the diameter of the pulmonary valve and branches of the pulmonary trunk. It should be considered as an alternative to shunt procedures in children with tetralogy of Fallot.