Ambulatory blood pressure monitoring (ABPM) has become a valuable tool for the evaluation of the borderline hypertension patient (Pickering et al., 1985; Weber & Drayer, 1984) just as the random daily monitoring of mood and cognitive states with Experience Sampling has provided insights into the experience of psychopathology (deVries, 1987). Ambulatory monitoring provides a glimpse of the circulatory system in dynamic action viewed from within the pattern of the patient's familiar daily life. Blood pressure readings taken in the unfamiliar setting of the physician's office are often unrepresentative of the patient's level of pressure outside the office (Perloff & Solokow, 1978). Perhaps for this reason, office readings are less closely related to target organ damage associated with elevated blood pressure than are ABPM readings (Perloff et al., 1983; Devereux et al., 1983).

Much of the variability in blood pressure in the active person is behaviorally induced (Pickering et al., 1982). These behavioral influences must be taken into account in interpreting BP readings. A systolic pressure of 150 mm Hg while climbing a flight of stairs is one thing. The same pressure while sitting quietly takes on a new meaning and appears in a new perspective.

Unlike ESM studies where behavior is recorded randomly throughout the day, in medical applications generally, fixed and physiologically linked monitoring sampling strategies have been the rule. In these studies, behavior is usually monitored by having the patient keep a behavioral diary on the day of monitoring.