This text deals with the methodological problems researchers have to face when trying to determine and study blood pressure (BP). It describes the measuring methods, the apparatus and the equipment used as well as the recording procedures and their technical shortcomings, together with their most common errors. It also deals with the various special problems involved. Ambulatory BP recording has greatly contributed to the significantly increased knowledge gained about the changeability of BP and the physiological, pathological and therapeutical factors which induce it. Even though, this technique may also have its limitations and may be subject to errors, its application is becoming more widespread, and its future enhancement will no doubt change the light under which we see BP today. I high BP recording is not only a sign on which the common AHT syndrome is normally diagnosed, but its prognosis value has also been known for years. Finally, because of the frequent epidemiological studies on BP, the prevalence of AHT in the various populations, likely therapeutical influences (therapeutical trials), etc., a close look at the methodological aspects of BP recording should be worth while considering.