The epidemic of overweight and obesity in youth is increasing the prevalence of prehypertension and hypertension among children and adolescents. The younger the child is at presentation and the more severe the blood pressure abnormality, the more likely a secondary cause of hypertension is to be present. Measurement of blood pressure in children requires adaptation to the age and size of the child. Interpretation must be related to normative values specific for age, sex, and height. Evaluation is primarily aimed at identifying secondary causes of hypertension, associated comorbidities, additional risk factors, and evidence of target-organ damage. Ambulatory blood pressure monitoring is emerging as a useful tool for evaluation of some patients, particularly for those with suspected 'white coat' hypertension. Management of prehypertension and hypertension is directed at the underlying cause, exacerbating factors, and the magnitude of the blood pressure abnormality. Healthy behavioral changes are a primary management tool for treating hypertension and, more particularly, prehypertension and for addressing other cardiovascular risk factors, such as obesity. Pharmacological management is reserved for patients with hypertension who do not respond to behavioral changes, have additional cardiovascular risk factors or diabetes, are symptomatic, or have developed target-organ damage.