Hypertension during childhood is not rare, with an estimated prevalence of between 1% and 2%, although it is often an underrecognized clinical entity. Elevated blood pressure may be a sign of underlying disease or it may represent early onset of essential hypertension. In recent years the measurement of blood pressure has been emphasized as an important component of the routine pediatric physical examination that enables early detection of children with hypertension. In the evaluation of the child with documented blood pressure elevation, confirmation of truly and persistently elevated blood pressure is of the utmost importance. In addition, a thorough history and a full clinical examination are essential. These are followed by appropriate investigations, which are tailored to the age of the child and to the severity of the blood pressure elevation. Investigations should not only focus on a search for the underlying cause, but also on establishing effects on target organs, complications or additional diseases and on assessment of the total cardiovascular risk to the individual patient. An algorithm, which is a valuable diagnostic tool for the diagnosis and management of the child with hypertension, is presented. All children with confirmed hypertension need long-term follow-up, counseling and treatment. In those cases where an underlying cause of the hypertension is detected, the established diagnosis then determines the specific therapy and management.