In the mid 1990s, Drs. Gerald Reaven identified a constellation of clinical findings, known variously as the metabolic syndrome, syndrome X, insulin resistance s- drome or insulin resistance-related disorders, that are associated with an increased risk of heart disease and diabetes. Interest in this topic grew rapidly, culminating in the publication by this series of the book, Insulin Resistance and the Metabolic Syndrome X, edited by Drs. Reaven and Laws in 1999. Since the original publication of that now classic volume, the world's population has continued to become more obese and sedentary and the prevalence of disorders related to insulin resistance has continued to increase throughout the developed and developing world. Of great concern in the last decade is the extension of these deleterious lifestyle patterns to the pediatric population, leading to both obesity and the appearance of insulin resistance-related disorders in youth as well as adults. Today, about one in three children and adolescents in the United States is overweight or obese, and this prevalence approaches one in two among adolescents in certain minority groups. In addition, components of this cardiovascular risk constellation are now being recognized in young adults, adolescents, and even children. Youth are increasingly developing type 2 diabetes, fatty liver disease, hypertriglyceridemia, hypertension, polycystic ovarian syndrome, sleep apnea, orthopedic and psychiatric complications, as well as other complications of obesity and insulin resistance.