Hypertension (HT) is an increasing problem in children, mainly because of the increasing prevalence of obesity. Unlike adults, the diagnosis of HT in children is based on the age, sex and height of the child. The overall prevalence is thought to be 1–5%. Measurement of blood pressure can be challenging in infants and young children. BP must be measured in the upper arm using an appropriate sized cuff. It is important to confirm automated oscillometric readings by a manual auscultatory method or by using a Doppler. The latter is particularly useful in infants. There is an increasing role for ambulatory BP monitoring in the diagnosis and also assessment of BP control.The aetiology of HT varies depending upon the age of the child, with renal parenchymal pathology being the predominant pathology in young children while obesity is the main cause in older children. The baseline investigations in all children include electrolytes, creatinine, urine dipstick and an ultrasound scan of the renal tract. Therapeutic lifestyle measures would be the initial treatment of choice for all patients with stage I hypertension. Pharmacotherapy is indicated if these measures fail or if there is stage II HT or evidence of target organ damage.