An intussusceptive antireflux valve was created in the Roux-en-Y loop at the same time as the hepatic portojejunostomy (Kasai procedure) for the purpose of preventing ascending cholangitis in 14 new cases of biliary atresia and in 6 long-term survivors of the Kasai operation after episodes of ascending cholangitis. Ascending cholangitis did not develop in any of the 13 new patients who showed bile outflow following a modified Kasai procedure with antireflux valve nor in 5 of 6 patients who had secondary valve implementation. Postmortem examination of a patient with a valve who died 2 years 3 months after surgery showed that the structure of the valve was intact and that the valve still was quite effective as an antireflux mechanism.