A 17-day-old infant with pyloric stenosis presenting with severe neonatal jaundice is described. The bilirubin level rose to 371 mumol/l and an exchange transfusion was considered. No history of frequent or forceful vomiting was given and the usual symptoms and signs of pyloric stenosis were absent. Radiographic studies revealed features typical of hypertrophic pyloric stenosis. At laparotomy a pyloromyotomy was performed and the jaundice subsided rapidly.