Cholestatic liver diseases including Alagille syndrome, alpha-1 antitrypsin deficiency, bile acid synthesis defects, biliary atresia, cystic fibrosis, mitochondrial hepatopathies, progressive familial intrahepatic cholestasis and primary sclerosing cholangitis, lead to significant morbidity and mortality in childhood, frequently necessitating liver transplantation. No single North American clinical center sees a large enough number of patients with these disorders to permit a rigorous approach to addressing unresolved questions including etiology and pathogenesis, optimal methods of diagnosis, and treatment, and factors that influence disease severity and prognosis. This competitive renewal proposal from the Baylor College of Medicine and Texas Children’s Hospital (BCM/TCH) seeks to continue ongoing research activities in the Childhood Liver Disease Research Network (ChiLDReN). The clinical center at BCM/TCH includes an outstanding group of clinician investigators with an extensive track record in synergistic translational and clinical research relevant to pediatric liver diseases. Performance to date in the on-going studies of ChiLDReN has been exemplary and has taken full advantage of a predominant market share of the population base of the Houston metropolitan region (5th largest in the United States) and the large referral patterns to TCH as a quaternary center for Pediatric Hepatology and Liver Transplantation. This renewal application includes a strong commitment to continuing the on-going research efforts including; 1) continuation of prospective longitudinal follow up of participants enrolled in ChiLDReN-based studies at BCM/TCH, 2) prospective enrollment of participants with biliary atresia in longitudinal studies either at the time of presentation with neonatal cholestasis or after diagnosis and 3) prospective enrollment of participants with primary sclerosing cholantitis in longitudinal studies either at the time of presentation with sclerosing cholangitis or after diagnosis. The overall hypothesis for these studies is that collaborative investigation will accelerate advances in pediatric cholestasis especially when rich clinical metadata can be leveraged with detailed imaging studies and a deep longitudinal biosample repository.