Abstract The mission of the UDN is to provide diagnoses to patients with undiagnosed phenotypes and advance research in the field of rare diseases. Since opening for applications in 2015 the Duke site has fulfilled this mission fully, achieving diagnoses for ~40% of participants, publishing more new disease gene discoveries than any other site in the Network, and delineating the psychosocial aspects of rare/ultra-rare disorders. These achievements have been possible due to our investment in a multi-disciplinary team of clinical and research professionals that focuses solely on achieving the goals of the Network and improving the lives of participants with rare or undiagnosed disorders. In this administrative supplement we will continue our work for new patients who are accepted into the Network for prior to June 30, 2022, but will be evaluated after that time (n=20). We will complete genomic sequencing and analysis, and we will identify and complete additional research tests as indicated in order to achieve diagnoses for our participants. We also will reevaluate the phenotypic and genomic data from active patients who remain undiagnosed from previous years (n= 120). All new and previously undiagnosed patients will be notified of the final status of their UDN evaluation and any pertinent results. We will continue to assess the psychosocial characteristics that are associated with living with, or having a child/family member with, an undiagnosed disease. Finally, we will continue to participate in Network activities, including the ongoing discussions regarding the structure, function and funding for the UDN beyond Phase II.