We have developed techniques to study endothellal function non-invasively in children and young adults. This programme of work will study how genetic and early enviromental factors affect endothellal function and other markers of early arterial disease (such as arterial stiffness) in a large population of pre-pubertal children undergoing long-term follow-up. Long-term follow-up will also show how these arterial changes progress during puberty and when later risk factors such as smoking are enocuntered.