Arterial hypertension (AH), either primary or secondary, is an important issue in childhood for its short- and long-term cardiovascular morbidity. Renal diseases are the most frequent causes of AH in children, but essential hypertension can also be detected early in life. It is important for blood pressure (BP) to be checked regularly (at least once every 5 years) in healthy children and adolescents and every year in those belonging to at-risk categories (family history of AH, low birth weight, obesity, etc). In children, AH is defined as BP recorded in three non-consecutive measurements with an appropriate device and cuff size > or = 95th centile for age, gender and height. Ambulatory BP monitoring is a valuable diagnostic tool and once AH is confirmed, a specific primary cause should always be ruled out (renovascular, cardiac, vascular, endocrine, pharmacologic, other). In case of border-line or significant AH (between 90th and 99th centile) a non-pharmacological treatment should be considered, whereas severe hypertension (>99th centile for height and age) will require pharmacological treatment (Diuretics, Angiotensin Converting Enzyme Inhibitors, Angiotensin Receptor Blockers, beta - and Calcium blockers).