Traditional sphygmomanometric techniques are heavily affected by the 'white-coat' effect and cannot be used to assess blood pressure variability over the 24h period. These limitations can be overcome in part using ambulatory monitoring, which (1) quantifies both the mean and the variability of blood pressure over 24h, including blood pressure fluctuations between day and night, (2) does not trigger any alerting reaction in the patient, (3) provides reproducible 24h blood pressure means and (4) allows the action of antihypertensive drugs to be assessed over 24h without interference from a placebo effect. Moreover, ambulatory blood pressure values are more closely related to the end-organ damage associated with hypertension than are isolated clinic readings. However, the limited accuracy of ambulatory monitoring in ambulant individuals, the lack of normal reference values for 24h blood pressure and the need for a longitudinal demonstration of the prognostic value of the technique do not permit the recommendation of its widespread use in clinical hypertension. Although the clinical use of ambulatory monitoring should be restricted to selected cases, there is general agreement on its usefulness in clinical pharmacology trials and in studies aimed at assessing cardiovascular regulation through the analysis of 24h blood pressure and heart rate fluctuations.