This retrospective epidemiologic study will investigate the hypothesis that parental occupational factors are associated with occurrence of Congenital Biliary Atresia (BA). Preliminary observation has raised suspicion regarding association with parental occupation, especially selected chemical exposures. Occupational and selected environmental factors reported by parents for the 6 months-preconceptual period, gestational trimesters, and neonatal period will be compared for cases and controls. This anomaly leads to progressive post-natal cirrhosis and debilitation, with death by age four in at least 60% of victims despite Kasai procedure surgery. Etiology is unknown and little studied epidemiologically, due to previous insufficient aggregates of cases. Principal objective is to determine whether reported chemical or other occupational employment of parents constitutes a significant factor associated with BA occurrence, or a subgroup thereof. Additional aims include determination of: 1. Associated selected home or avocational exposures. 2. Whether teratogenic associations are related to paternal or maternal exposure(s), or to specific combined exposures (interactions). 3. Increased incidence of other teratogenic outcomes (including spontaneous abortion) in case sibships (correlated with parental occupation for each pregnancy). 4. Associated familial occurrence of hepatitis (B and other), and other specific conditions. 5. Maternal health status and perinatal complications. 6. Selected demographic and socioeconomic variables. Consecutive cases (n = 400), both living and deceased, from infancy to pre-school aged, will be obtained from the National BA Registry of the American Academy of Pediatrics. Regional, age, and time-matched controls will be selected from each respective case surgeon's files to provide approximate case-control equivalence on temporal and geographic variables. Case diagnoses will be validated by review of selected medical reports. Data on outcome and potentially confounding variables will be obtained through in-depth phone interview with parents. Distribution and cross-tabulations of various occupations, occupational groupings (based on similar chemical exposures), and other environmental factors will be done by case-control status, after adjustment for potential environmental, socioeconomic, and pre-perinatal confounders. Multiple regression analysis will be used to weigh significant variables, identify significant interactions, and adjust for confounding variables.