ABPM is a standard technique in adult antihypertensive trials to study the magnitude and duration of effect of investigational drugs. These methods are needed for pediatric studies. Before such methods can be developed, preliminary information must be collected to demonstrate that the device can be used for antihypertensive studies in children (i.e, to determine the dropout rate following the first ABP study, to determine the frequency of white coat hypertension in a selected population, to compare casual (office) blood pressures commonly used to diagnose hypertension in children with those obtained by ABPM, and to assess the placebo effect in children with borderline and mild hypertension).