An intussusception-type antireflux valve was created in the Roux-en-Y loop in 23 infants with biliary atresia (17 new cases, and six others after episodes of ascending cholangitis) and 10 patients with congenital bile duct dilatation, in order to prevent ascending cholangitis after hepatic portojejunostomy. Mesenteric blood vessels were divided in a 4 cm length of the Roux-en-Y loop, and the distal 1.5 cm of this portion was further denuded of the seromuscular layer; an antireflux valve was thus established by invaginating the proximal portion into the denuded jejunum. No case, in which this technique was used, was associated with any surgical complications, and ascending cholangitis never developed in any of the 17 new cases with biliary atresia, during an average follow-up of 32 months.