BACKGROUND: Increased age at surgery has a negative impact on results of the Kasai operation for biliary atresia in infancy and early childhood. It remained unclear if an age threshold exists and if this effect persists with extended follow-up. In this study we examined the relationship between increased age at surgery and its results in adolescence. METHODS: All patients with biliary atresia who were living in France and born between 1986 and 2002 were included. Median follow-up in survivors was 7 years. RESULTS: Included in the study were 743 patients with biliary atresia, 695 of whom underwent a Kasai operation; 2-, 5-, 10-, and 15-year survival rates with native liver were 57.1%, 37.9%, 32.4%, and 28.5%, respectively. Median age at Kasai operation was 60 days and was stable over the study period. Whatever the follow-up (2, 5, 10, or 15 years), survival rates with native liver decreased when age at surgery increased ( ≤ 30, 31-45, 46-60, 61-75, and 76-90 days). Accordingly, we estimated that if every patient with biliary atresia underwent the Kasai operation before 46 days of age, 5.7% of all liver transplantations performed annually in France in patients younger than 16 years could be spared. CONCLUSIONS: Increased age at surgery had a progressive and sustained deleterious effect on the results of the Kasai operation until adolescence. These findings indicate a rational basis for biliary atresia screening to reduce the need for liver transplantations in infancy and childhood.