Blood pressure (BP) in children and adolescents is associated with their growth. BP is most strongly associated with height during height gain and with degree of obesity after reaching final height. BP in childhood and adolescence is correlated with BP in adulthood. The pathophysiology of pediatric essential hypertension is associated with obesity, excess salt intake, and a low birth weight. The common causes of pediatric secondary hypertension are renal parenchymal and renovascular diseases. The significance of diagnosing pediatric hypertension involves detecting secondary hypertension and preventing organ damage due to hypertension as well as tracking essential hypertension in adulthood. Appropriate BP measurement procedures are required for diagnosing pediatric hypertension. The inflatable bladder of an appropriately sized cuff should exceed 40% of the arm circumference. BP measurements should be performed consecutively at least 3 times using an appropriately sized cuff. The diagnosis of hypertension requires that all BP values measured on 3 or more occasions be above the reference value. The criteria for pediatric hypertension are determined based on the distribution of BP in healthy children and adolescents, with values above the 95th percentile of normal representing hypertension. Japanese criteria define pediatric hypertension as ≥120/70 mmHg for preschool children, ≥130/80 mmHg for 1st–3rd graders, ≥135/80 mmHg for 4th–6th graders, ≥140/85 mmHg for 7th–9th grade boys, ≥135/80 mmHg for 7th–9th grade girls, and ≥140/85 mmHg for senior high school boys and girls. The prevalence of Japanese pediatric hypertension was 0.9% based on proper measurement protocols. The basis of managing pediatric essential hypertension is healthy lifestyle modifications. Pharmacotherapy is indicated for persistent hypertension, symptomatic hypertension, secondary hypertension, the development of target organ damage, the presence of chronic kidney disease, and diabetes mellitus. Screening for pediatric hypertension is important; therefore, BP should be routinely measured in children and adolescents.