The insulin resistance syndrome (IRS) is associated with a considerable increase in the risk of cardiovascular disease in adults. The disorder most likely is inherited to some degree with onset in childhood and early adolescence. The IRS is best defined by quantitative data from euglycemic insulin clamp studies. The investigators have developed a unique data base in children, and by continuing repeated studies and follow-up in early adulthood together with studies in parents and siblings this study should provide important insight into the occurrence and progression of cardiovascular disease in later life.