Type 1 diabetes is a common chronic disease of childhood. It is not yet preventable. Multiple daily injections of insulin, tests of blood sugar, and careful dietary planning are required lifelong to prevent long-term complications such as blindness and kidney failure. Recent studies of potential risk factors in children with diabetes, along with studies revealing the immunologic properties of vitamin D, and experiments in animals suggest higher doses of vitamin D may prevent type 1 diabetes. For proof for human children, a randomized trial will compare groups at risk randomly assigned to receive either the usual vitamin D supplement or a higher amount, 2000 IU daily. This initial study is a small scale test of procedures.