This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ABSTRACT HYPOTHESIS 1. Environmental/epidemiological/genetic factors contribute to the pathogenesis of cholestatic liver diseases in children. 2. Ultrasonographic findings at diagnosis are specific for the diagnosis of biliary atresia. 3. Clinical parameters, such as laboratory values, (e.g. total bilirubin at 6 months post-surgery), the development of various clinical findings (e.g. ascities), are predictive of the evantual outcome of the Kasai Portoenterostomy by 2 years of age. Developmental delay can be predicted based upon serial clinical (e.g. growth failure) or laboratory values (e.g. total bilirubin). SPECIFIC AIMS Specific Aim 1: To establish a prospective database with demographic and clinical information about infants with cholestatic disease and their families. Specific Aim 2: To establish repositories for blood, urine, bile, and tissue samples from these children and their first-degree relatives. Specific Aim 3: To prospectively follow these children over time to characterize the natural history of the disease. Specicic Aim 4: To identify risk factors (such as, environmental, infectious and genetic risk factors) related to onset, to outcome and to the success of treatment(s) for the different cholestatic diseases, with special emphasis on biliary atresia.