Subjects were enrolled from 1987-1992 and were followed from diabetes diagnosis. Standardized protocols for examinations and interviews were implemented and the data base included a valuable longitudinal plasma bank. Because incident cases were enrolled, information was collected from diagnosis on children, adolescents and young adults currently without symptoms of atherosclerosis. The existing database was expanded, the existing resources were used including the plasma bank, and promising new and well established clinical research techniques were incorporated by: (i) measuring plasma lipid levels on stored plasma and on newly collected blood samples, (ii) measuring triglyceride levels on newly collected blood samples, (iii) measuring urinary albumin excretion rates on newly collected specimens (already measured from diagnosis to date), and (iv) assessing endothelial function by brachial artery ultrasound, (v) measuring the intima medial thickness (IMT) of the carotid artery by ultrasound, and (vi) measuring coronary calcium by computed tomography scanning. These activities allowed pursuit of the following specific aims: 1) to determine the relationship between established risk factors for atherosclerosis and the development of pre-clinical atherosclerosis, 2) to determine the relationship between endothelial dysfunction and carotid IMT, and 3) to determine the relationship between coronary artery calcification and carotid IMT. Such information was critical in directing further efforts toward primary prevention of atherosclerosis in individuals with Type 1 diabetes mellitus.