 Many published studies reveal that adult patients with T1DM can have early, silent and more advanced vessel wall thickness than normal subjects. This is influenced by the degree of their blood sugar control. If this is happening in adolescents, we want to know what proportion of adolescent children with type 1 diabetes show signs of early blood vessel damage. We also want to learn if these signs of damage are linked to other factors such as how long someone has had diabetes, blood sugar control or individual differences because of a difference in genetic make-up. 