A state of the art metabolomics core will be a vital part of the Undiagnosed Diseases Network (UDN). However, in order for the UDN to realize its the full potential it is essential that the metabolomics core doesnt simply function as a high tech referral lab. We propose the formation of a partnership that will combine the state of the art analytical capabilities of the Pacific Northwest National Laboratory (PNNL), with clinical, genetic, and bioinformatics expertise from Oregon Health & Science University (OHSU), to create a metabolomics core that functions as a fully integrated component of the network. The integration of this combined expertise will facilitate the linkage of novel metabolites or patterns of metabolites identified by the metabolomics core to the underlying metabolic and genetic derangements, as well as clinical signs and symptoms, and to translate this knowledge into specific clues regarding the genetic etiology of the patients disorder. The following specific aims describe the approach we will use to create the UDN Metabolomics Core (UDNMC).