Ambulatory blood pressure (BP) monitoring is a technique associated with several operational characteristics that make its use in adult hypertension trials attractive. To extend its use effectively to hypertension trials in children, additional studies are needed to assess its performance in this population. It is likely that ambulatory monitoring will be important in this population for the study of drug efficacy and safety. In general, ambulatory monitoring has better short-term and long-term reproducibility than office BP. Some data suggest that this superiority of ambulatory over office BP is also true in children. This better reproducibility should allow a drug effect to be detected with a smaller sample size, especially in crossover studies. Ambulatory BP averages are also free from the office-induced increase in BP, making it is easier to include adults and children in trials who have ambulatory hypertension. Such a requisite for a trial has to be planned to include more patients in the recruitment and run-in phases as use of an ambulatory criterion for hypertension will lead to some patients with elevated office BP not qualifying based on ambulatory readings. Of additional major importance, ambulatory monitoring of BP correctly identifies the temporal effects of a drug and hence allows accurate calculation of its trough-to-peak ratio. Ambulatory monitoring promises to be a significant tool for the study of hypertension in children including pathophysiology and the efficacy of antihypertensive drugs.