This application is designed to establish a center for the Diabetes Control and Complications Trial (DCCT) at the University of California, San Diego (UCSD). This trial is a multi-center trial funded by the National Arthritis, Diabetes, and Digestive and Kidney Diseases branch of the National Institutes of Health designed to provide a definitive answer to the question as to whether or not excellent glycemic control prevents and/or ameloriates the late complications of Type I diabetes. If selected, the UCSD Center of the DCCT will be expected to recruit, screen and enter 30 suitable subjects into the study over a 2-year period and then provide the designated follow-up care until the biostatistician announces that statistical power has been achieved in terms of answering the question. Since it is anticipated that at least 7 years will be required to achieve this goal, the UCSD will also need to assume the follow-up care of a number of subjects enrolled elsewhere who relocate to the San Diego catchment during the course of the study. The study is being conducted under a standardized protocol during a feasibility study recently completed.