Type 1 diabetes mellitus arises in genetically predisposed individuals as a consequence of immune mediated destruction of the pancreatic islet insulin secreting beta cells. The onset of clinical symptoms of diabetes represents the end point of a chronic progressive decline in beta-cell function and occurs when the majority of beta-cells have been lost. The Diabetes Prevention Trial for Type 1 Diabetes (DPT-1) has been conducting studies to determine whether early intervention using antigen-based therapies (parenteral or oral insulin) in nondiabetic relatives of persons with Type 1 diabetes can delay the development of Type 1 diabetes as a clinical disease and to conduct long term follow-up of subjects developing diabetes. It is recognized that it is likely to be necessary to assess multiple intervention strategies in different cohorts of individuals before the disease process leading to Type 1 diabetes can be completely interrupted. To that end, Type 1 Diabetes TrialNet creates an expanded national diabetes trial network of cooperative clinical research groups and support facilities. It is envisioned that TrialNet will conduct pilot and expanded studies to evaluate new approaches to prevent or ameliorate Type 1 diabetes, natural history and genetics studies in populations screened for or enrolled in these studies, and other studies that may result in an improved understanding of Type 1 diabetes and the prevention of the disease. This application seeks to provide the core support facilities and infrastructure to complete the DPT-1 protocols and achieve their objectives and to provide Type 1 Diabetes TrialNet appropriate experienced core support facilities. The applicant has been the Operations Coordinating Center (OCC) and, through a subcontract, the Data Monitoring Unit (DMU) for DPT-I since its inception, providing administrative, statistical and operations support; and coordinating other core facilities, including core laboratories (to assure standardized, reliable methods), compounding and dispensing pharmacies, and public relations support. That network developed for DPT-1 provides the platform on which to build the enhanced infrastructure for Type 1 Diabetes TrialNet. Thus, these core facilities provide the basic structure for an ongoing series of clinical trials in TrialNet. This application describes an experienced team that is expert in the design and conduct of multi-institutional diabetes prevention trials, established policies and procedures, and an outstanding working relationship with clinical centers to meet the needs of TriaINet.