Background: - Family and twin studies have suggested that genetic factors influence approximately 50 percent of a person's susceptibility to type 2 diabetes. Recently, some of the genes involved in the development of type 2 diabetes have been identified, in large part by genome-wide association studies. Certain risk factors for type 2 diabetes, such as obesity and insulin resistance, are highly inheritable, as are diabetic complications such as diabetes-related eye and kidney disorders. However, few genes associated or linked with diabetes risk factors or complications have been conclusively identified, and more research is needed to study specific genetic factors associated with these aspects of diabetes. Objectives: - To identify and characterize genetic variants associated with type 2 diabetes, its risk factors, and its complications. Eligibility: - Individuals at least 18 years of age who are not pregnant or nursing mothers at the start of the study. Design: * All participants will provide information about family history, ethnicity and ethnic background, occupation, behavioral risk factors, and other data as requested by the researchers. * In addition to a general health history, participants will provide specific information about diabetes history, with particular emphasis on date of diagnosis, symptoms, initiation of insulin therapy, complications, and current medications. * Testing procedures will be different for individuals with and without diabetes. Those without diabetes will have an oral glucose tolerance test, while those with diabetes will be examined for diabetic complications. * Other tests during the study will include the following: * Physical examination with measurements of height and weight, waist circumference, blood pressure, and other tests for individuals who have been diagnosed with diabetes * Glucose tolerance test for those who have not been classified as having diabetes * Retinal photographs * Electrocardiograms * Hepatic Ultrasound * Blood and urine tests * Depending on the results of the examination and laboratory findings, participants may be asked to return to the clinic for supplemental interviews, physical examinations, or blood tests, or to arrange referrals for medical evaluation and treatment. * Participants who have diabetes will be asked to return for yearly follow-up visits. Participants who do not have diabetes at the initial examination will be asked to return for follow-up visits every 2 years.