Purpose: The aim of this study was to review the biliary complications occurring in late follow-up after liver transplantation in children. Methods: The medical records of 135 children who received orthotopic liver transplantations (OLT) and had graft survival of more than 1 year were reviewed. Technical variants using a reduced-size graft were applied in 32 (23.7%). For biliary reconstruction, 15 patients had choledachocholedochostomy and 120 a Roux-en-Y loop. Biliary reoperation in the early post-OLT period was needed in 24 patients (17.7%). Routine checking of liver function and duplex Doppler ultrasonography (DDS) were performed during the follow-up period, which averaged 58 months. Late biliary complication was defined as that occurring after the first hospital discharge. Results: Late biliary complications occurred in 1.8 children (13.3%); 16 showed symptoms or analytical disturbances in liver function tests. The Diagnoses included uncomplicated cholangitis (n = 6), anastomotic biliary stricture (n = 7), ischaemic damage of the biliary tree (n = 3) including one late (28 months) hepatic artery thrombosis leading to an intrahepatic biloma. and bile leak after T-tube removal (n = 2). The six children with uncomplicated cholangitis had no repeat episodes in follow-up despite persistent aerobilia. Six patients affected by anastomotic strictures were treated successfully with percutaneous dilatation and, if present, stone removal. Persisting dysfunction and cholangitis occurred in one case affected by ischaemic biliary disease. Biliary leaks after T tube removal settled spontaneously. Risk factors for late biliary com plications were determined. There was no relation to the cold ischaemia time, type of graft or biliary reconstruction, or previous early post-OLT biliary reoperation. Aerobilia (affecting 21.5% of OLT patients) was related to cholangitis (P = .001). Conclusions: Anastomotic strictures, reflux of intestinal contents via the Roux-en-Y loop, and residual ischaemic damage led to late biliary complications in 12% of paediatric OLT patients. Evidence of biliary dilatation on DDS may be delayed in anastomotic strictures; in these cases the results of percutaneous treatment were excellent. Children with aerobilia have and increased risk of cholangitis. J Pediatr Surg 34:316-320. Copyright (C) 1999 by W.B. Saunders Company.