Extrahepatic biliary atresia is a liver disease presenting in early infancy, manifested by progressive obliteration of the extrahepatic bile ducts. It has been estimated to occur in from one per 8000 to one per 15000 live births, and is the single most common indication for performance of liver transplantation in children. None of the incidence figures is based on a well defined geopolitical region; most estimates of the frequency of this condition are derived from referral centers. Some investigators have suggested a time-space clustering of this condition. This project will gather birth cerificates and other information on all cases occurring among children born over a period of 12 years in Ohio. Cases will be compared to the other births in the state for evidence fo changes in incidence and clustering.