Ambulatory blood pressure monitoring (ABPM) is a new technique recently introduced into paediatrics. Devices with auscultatory blood pressure measurement may be more precise but give more erroneous readings than those with oscillometric measurement. For the interpretation of the results, mean day- and night-time values should be calculated according to patients' diaries and gender- and height-specific percentiles for ABPM measurements should be used to define hypertension. The use of "blood pressure load" as the percentage of single readings above a given upper level is not standardised in children and adolescents. A nocturnal blood pressure decline of less than 10% is defined as "non-dipping", although this is an arbitrary definition whose prognostic value is not evaluated in paediatric patients. Several studies showed that ABPM in children is superior in detecting "white-coat''-hypertension, shows a better reproducibility and is a better prognostic factor for left ventricular mass compared to casual blood pressure measurements. Clinical studies show the value of ABPM in obese children, in children with renal diseases, on dialysis therapy and after renal transplantation as well as in diabetic children or in children after surgical repair of aortic coarctation. Ambulatory blood pressure monitoring in children and adolescents has grown to a valuable method for the daily management of patients with suspected or established hypertension. However, there is still a lot of work before all technical problems are solved and international guidelines can be published which are based on evidence from follow-up studies.