Biliary atresia is a disease of unknown etiology but not usually thought to have a significant genetic predisposition. We report 5 infants with various forms of chromosome 22 aneuploidy as follows: 2 infants who have classical cat-eye syndrome, 2 who have partial duplication of chromosome 22 (supernumerary der(22) syndrome), and 1 who is mosaic for trisomy 22. All of these infants had significant congenital bile duct anomalies (specifically biliary atresia, n = 4)-that was the most important component of their clinical presentation. We consider whether this has possible implications about the genetic contribution to the etiology of biliary atresia.