Hypertension (HT) in children and adolescents is an important pathology, associated with modi fiable and non-modifiable factors. In the pediatric, the prevalence of HT is around 3.5%, and it in creases progressively with age. The ideal method for diagnosis is the measurement of blood pressure (BP) with auscultatory instruments. As published by the American Academy of Pediatrics (AAP), BP should be measured in children over 3 years of age once a year, and in children under 3 years of age, if it presents risk factors. Once HT has been confirmed, the evaluation should be directed towards the detection of a causative disease and the search for risk factors associated with primary HTN. The goal of treating primary and secondary HTN in pediatrics is to achieve a level of BP that decreases the risk of target organ damage. The therapeutic options include: treatment according to specific etiology, non-pharmacological and pharmacological. This document is the product of a collaborative effort of the Nephrology Branch of the Chilean Society of Pediatrics with the aim of helping pediatricians and pediatric nephrologists in the diagnosis and treatment of hypertension in childhood. In this first part, the recommendations of the diagnosis and study are presented.