Hypertension is one of the most common health problems in the United States and a powerful independent risk factor for cardiovascular and renal disease. Until recently, the incidence of persistent hypertension in children has been low, with a range of 1% to 3%. Recent data indicate that over the last decade, however, average blood pressure levels have risen substantially among American children. Obesity and other lifestyle factors, such as physical inactivity and increased intake of high-calorie, high-salt foods, are thought to be responsible for this trend. Hypertension in children is currently recognized as an important health issue. There is increasing evidence that hypertension has its antecedents during childhood, because adult blood pressure often correlates with childhood blood pressure. Hypertension in children also is viewed as a significant risk factor for the development of cardiovascular disease in adulthood.