LEARNING HEALTH SYSTEM CORE ABSTRACT Current pediatric care relies too much on expert consensus or extrapolation from limited data; major gaps exist in the quantity and quality of evidence that informs clinical decision-making. Clinical research as currently practiced generates evidence slowly and at high cost. One of the critical barriers to studying childhood kidney disease is the lack of a national interconnected, multi-institutional infrastructure able to reach adequate numbers of affected children and provide the depth of information necessary to adequately characterize their kidney disease. PEDSnet, a national multi-specialty collaboration across eight pediatric academic centers, was created to address these challenges by developing a national digital architecture to rapidly implement learning health systems (LHS) across multiple pediatric conditions. It has focused on using the increasing adoption of certified electronic health records to integrate research performed in routine care settings, capture structured data at clinical encounters, promote quality improvement processes, and increase patient engagement in improving child health. Successes to date demonstrate both the will and capacity of participating institutions to extend the work of PEDSnet to formally establish a Pediatric Nephrology Learning Network in order to address fundamental questions of clinical effectiveness for children and their families. Our application benefits from these robust pre- existing resources and a unique history of collaboration by children?s hospitals that has already made tremendous progress in building a national infrastructure to expedite pediatric research. The expertise, methods, and data infrastructure developed by PEDSnet will serve as the centerpiece of the Pediatric Center of Excellence in Nephrology (PCEN) LHS Core. Specifically, the LHS Core will address the following aims in order to advance the Pediatric Nephrology Learning Network: (1) Establish the organizational architecture and governance of the Pediatric Nephrology Learning Network; (2) Extend PEDSnet resources to construct, maintain, and mediate access to structured data as part of a new Pediatric Nephrology Database Resource; (3) Develop capacity to address unstructured data elements in the Database Resource through knowledge extraction from pediatric kidney biopsy reports; and (4) Stimulate high quality research using the newly developed Pediatric Nephrology Database Resource, by providing shared technical and methodological resources for use across the research development continuum. Implementing a LHS dedicated to children with kidney disease closely aligns with the overall goal of the PCEN to facilitate extensive collaborative research around the causes, diagnoses, and treatment of kidney diseases in children, with increased efficiency and effectiveness. If the proposed activities are successfully executed, we will have forged an organizational architecture and leadership structure, created a uniquely valuable data resource, and developed a functional infrastructure that makes cross-institutional collaboration amongst investigators in pediatric nephrology research routine, with few barriers to interaction and implementation of pragmatic clinical trials.