This study was based on the follow-up of 55 patients with tetralogy of Fallot and operated for branch pulmonary artery stenosis. Twenty two patients were followed up clinically (Group I): 91% of the patients were asymptomatic at the end of the first operative year. Thirty three patients (Group II) underwent control catheter studies after an average of 2.5 years after complete repair: only 70% of these were asymptomatic at 1 year; 8 were reoperated after an average of 3.6 years. The surgical result could only be evaluated by control catheter studies. The results were therefore based on the data obtained from Group II: this selection resulted in a pessimistic bias as the outcome in the two groups was significantly different. The stenoses were congenital and/or iatrogenic. They were located on the left branch (55%), the right branch (9%), the bifurcation (24%), separately on the two branches (12%). The diversity of the operative techniques and materials used reflects the difficulty of this surgery. The cumulative results were good in 33% of cases, average in 28% and poor in 39%. The results were better in isolated branch stenosis than in stenosis of the bifurcation, though not statistically significant. The results were related to age, body weight, the type, the site, the length, the association of stenoses and the material used. Significant predictive factors for a good result were: Gore-Tex (p less than 0.05) and pericardial pedicle (p less than 0.005). The average follow-up of patients with the latter type of patch was only 2 years. These results require confirmation by studies of larger numbers of patients followed up for a longer period.