The NIDDK conducts and supports much of the clinical research on the diseases of internal medicine and related subspecialty fields. Many of the large clinical studies funded by the NIDDK collect biospecimens from subjects for analysis and future study. The collection of these patient and control samples from many different studies in a single repository is a valuable resource with which researchers can rapidly validate clinical hypotheses and algorithms for clinical decision. The collection is also advancing the development of prognostics, markers, and therapeutics for diseases related to the mission of the NIDDK. Discovery of disease related genes requires a population of individuals with the genetic variant, as well as a population of control (unaffected) individuals. Thus, a repository of genetic materials, including DNA samples, cryopreserved lymphocytes, immortalized cell lines, and accompanying clinical and pedigree data is clearly an invaluable resource for the research community studying diseases related to the mission of the NIDDK. The repository will allow the continued storage, maintenance, and quality control, and equitable, ethical distribution of DNA and other resources important to the study of diseases under the mandate of the NIDDK. It facilitates sharing of resources, thus encouraging work by a broad group of investigators and, perhaps, increasing the sample size and the resulting power of a study to identify genetic determinants of a disease. It helps to ensure that research participants will be making a maximal contribution, and decreases duplicative sampling efforts. This project, continues an important collection begun in 2003 and is conceptually related to repositories in existence at other institutes at the NIH.