The Diabetes Control and Complications Trial/Epidemiology of Diabetes Inter-

ventions and Complications (DCCT/EDIC) study continues to address knowledge gaps in our understanding of type 1 diabetes and the effects of intensive therapy on its long-term complications. RESEARCH DESIGN AND METHODS During the DCCT (1982–1993), a controlled clinical trial of 1,441 subjects with type 1 diabetes, and the EDIC (1994–present), an observational study of the DCCT co-hort, core data collection has included medical history questionnaires, surveil-lance health exams, and frequent laboratory and other evaluations for microvascular and macrovascular disease. Numerous collaborations have ex-panded the outcome data with more detailed investigations of cardiovascular disease, cognitive function, neuropathy, genetics, and potential biological path-ways involved in the development of complications. RESULTS The longitudinal follow-up of the DCCT/EDIC cohort provides the opportunity to continue monitoring the durability of intensive treatment as well as to addres