A postal survey identified 114 infants with biliary atresia (roughly one in 21 000 live births). Biliary operations were performed on 107. Of the 105 infants who were followed up, 35 were free of jaundice at 10 months to 3 1/2 years. Good results occurred most often in those operated on by 12 weeks and were also related to the number of cases operated on in each centre. Only two of 18 infants treated in centres dealing with one case a year were free of jaundice compared with 11 of 38 at centres treating two to five cases a year and 22 of 49 in a centre treating more than five cases a year. Jaundice in an infant of more than 2 weeks associated with yellow urine or pale stools is never physiological and requires urgent investigation to identify causes for which effective treatment may be possible. Identification of suspected cases by 4 weeks of age and a greater concentration of investigative and surgical skills should improve the short term results of surgery and the long term prognosis of biliary atresia.