There is a widely held but unsubstantiated belief that in infants with biliary atresia and coexisting polysplenia syndrome, the Kasai operation fails. An equally poor prognosis has been forecast for patients with this complex treated by liver transplantation. From 1975 to 1989, 16 of 131 infants with biliary atresia (12%) had one or more components of the polysplenia syndrome: polysplenia (8), intestinal malrotation (12), preduodenal portal vein (6), absent inferior vena cava (6), aberrant hepatic artery (4), or abdominal heterotaxia (4). Although technically more demanding, 12 of the 15 polysplenia patients achieved biliary drainage after operation. (One patient had exploration only, because of parental preference). Four children are alive; two are anicteric and well at ages 5 and 8 following Kasai's operation, and two by virtue of liver transplantation done at ages 4 and 7. Three of the five patients who had liver transplantation died. Acturial survival was 44% at 5 years, not significantly different from that of the 115 nonpolysplenia patients (48%). When associated with the constellation of anomalies known as the polysplenia syndrome, biliary atresia is most likely caused by an early (at approximately the fifth week) embryonic insult. The anomalies do not preclude successful biliary reconstruction using the Kasai procedure or successful liver transplantation.