- The major criteria for eligibility included insulin dependence, as evidenced by deficient C-peptide secretion; an age of 13 to 39 years; and the absence of hypertension, hypercholesterolemia, and severe diabetic complications or medical conditions. To be eligible for the primary-prevention cohort, patients were required to have had insulin dependent diabetes mellitus (IDDM) for one to five years, to have no retinopathy as detected by seven-field stereoscopic fundus photography, and to have urinary albumin excretion of less than 40 mg per 24 hours. To be eligible for the secondary-intervention cohort, the patients were required to have IDDM for 1 to 15 years, to have very-mild to moderate nonproliferative retinopathy, and to have urinary albumin excretion of less than 200 mg per 24 hours.