The Common Fund’s Undiagnosed Diseases Network (UDN) is a research study to improve the level of diagnosis of rare and undiagnosed conditions. In the United States, it has been estimated that approximately 25 million Americans suffer from a rare disorder. The UDN established a nationwide network of clinicians and researchers who use both basic and clinical research to uncover the underlying disease mechanisms associated with these conditions. In its first 20 months, the UDN accepted 601 participants undiagnosed by traditional medical practices. Of those who completed their UDN evaluation during this time, 35% were given a diagnosis. Many of these diagnoses were rare genetic diseases including 31 previously unknown syndromes. The UDN is currently accepting participant applications(link is external)..Five new clinical sites, a new metabolomics core, and increased model organism capabilities among additions.