This is a competing continuation application for the Pediatric Cardiomyopathy Registry (PCMR), an NHLBI program that has registered and analyzed 2920 children with cardiomyopathy. The underlying incidence, prevalence, and etiologies of cardiomyopathies are currently under study. In the current grant application, there will be three Specific Aims. The first expands on the natural history of cardiomyopathy and transplantation by integrating the PCMR and the Pediatric Heart Transplant Study databases in order to examine whether and how cardiac transplantation modifies the clinical course of cardiomyopathy in children. The second specific aim focuses on the functional status of pediatric cardiomyopathy patients. We propose to establish the longitudinal course of functional status in children with cardiomyopathy, and analyze the relationship to clinical events and outcomes. This will be accomplished by assessment of the functional status of pediatric cardiomyopathy patients, including the subset of children undergoing heart transplantation, by continuation of the current PCMR Functional Status Substudy and extension of the study to children in the post-transplant-period period. The third specific aim relates to viral and genetic testing and will investigate how genetic and viral markers of cardiomyopathy are associated with clinical and functional outcomes. We will collect cardiac tissue and blood samples from 300 children with cardiomyopathy for viral genome and genetic screening 9G4.5 gene) using the Pediatric Cardiomyopathy Repository, and correlate the results to clinical outcome. These studies will dramatically increase our understanding of pediatric cardiomyopathy, suggest new areas of research and improved patient management.