Eight infants between the ages of one and three months with prolonged conjugated hyperbilirubinaemia had duodenal aspirations performed to differentiate between biliary atresia and neonatal hepatitis. Four infants had bile-stained aspirates and in all of them the jaundice subsided completely by eight months of age. We have found duodenal aspiration a safe, inexpensive and simple procedure to undertake in helping us make a rapid differentiation between patients with conjugated hyperbilirubinaemia requiring urgent laparotomy and those that do not require surgery. This approach appears to be reliable although further studies need to be undertaken.