The goal of this commentary is to review the most relevant topics concerning the clinical utility of ambulatory blood pressure (BP) monitoring, such as the state of the art "reference BP values", the importance of the discrepant situations between office and ambulatory BP (white-coat and masked hypertension) and those of the recommended clinical indications to now. From a small number of studies, operational thresholds to define hypertension have been established. They are useful tools even though more studies are necessary to create strong reference values. Ambulatory BP measurement is increasingly recognized as being indispensable to the diagnosis and management of hypertension, and it has contributed significantly to our understanding of hypertension by revealing or "unmasking" BP phenomena that were not readily apparent using traditional techniques of measurement in clinical practice. Ambulatory BP monitoring should be performed in adolescents with either office mild essential hypertension before starting antihypertensive drug treatment or a strong family history of hypertension or an early cardiovascular event. Obese children with normal office BP values will also benefit from ambulatory BP monitoring. Other indications are the assessment of refractory hypertension or drug-induced hypotension. Finally, additional BP information in chronic renal failure, diabetes, and autonomic neuropathy can be obtained by using ambulatory BP monitoring.