Concept of smooth 24-h blood pressure control: Smooth 24-h blood pressure control is an obvious goal of antihypertensive therapy, but it is difficult to measure and its clinical impact is difficult to verify. The term 'smooth' is of uncertain significance. Clearly, normal 24-h blood pressure varies between resting periods and periods of activity. If, however, the concept means, as commonly used, that in treated hypertensives blood pressure during the 24-h period should be superimposable on the daily blood pressure values and fluctuations in normotensive subjects, then the concept is valid. But this definition raises the even more complex and difficult issue of how to define hypertension and normotension. Attempt to define normal ambulatory blood pressure values: An attempt to establish normal reference values for ambulatory blood pressure in an epidemiologic context is underway. Preliminary data from the PAMELA study indicate that both 24-h means and home blood pressure values are several millimeters of mercury lower than clinic blood pressures. In order to identify the ideal blood pressure profile to be achieved by therapy, there are two additional aspects to be clarified. One is whether it is daytime or night-time blood pressure that should be more effectively normalized by treatment; the other is whether a reduction in blood pressure variability should also be among the goals of antihypertensive treatment. CONCLUSIONS Despite expanding use of ambulatory blood pressure monitoring and increasing information on blood pressure profiles during treatment, we are still far from fully understanding the impact of ambulatory blood pressure monitoring on the management of hypertension.