Genetic factors are significant determinants of both Type 1 and Type 2 diabetes mellitus. They are also responsible, in part, for susceptibility to late diabetic complications. Identification of the nature of these factors is now feasible given recent advances in molecular genetics. The objective of this Core is to promote and facilitate genetic studies of diabetes and its complications in humans and animal models at the Joslin Diabetes Center and other collaborating institutions. Achievement of this objective requires resources in the form of repositories of DNA and support services for genetic studies. During the next funding period, the Genetics Core will maintain the resources and services established during the previous cycle, add new repositories and develop new services in molecular genetics and data analysis. The following are the Specific Aims for the next funding period: 1. Expand and maintain the existing panels of DNA so that these can be used by investigators from the Joslin Diabetes Center as well as other collaborating institutions. 2. Establish new panels of DNA samples to be made available to other investigators. 3. Provide technical support services to facilitate genetic studies on humans at the Joslin Diabetes Center as well as collaborating institutions. 4. Develop new technical support services for genetic studies on animal models of diabetes. Maintenance of these capabilities and achieving the goals for enlarging the resources of the Genetics Core will be critical for the growth of molecular genetic studies at the Joslin Diabetes Center. First, the Core will eliminate duplication/competition in the collection of samples for genetic studies. Second, the existence of readily available resources for genetic studies will attract new fellows and investigators to conduct molecular genetic studies in humans and animal models of diabetes. Third, by providing in-house expertise, the Core will have a favorable impact on the design of genetic studies and analysis of genetic data.