A blood pressure (BP) recording is, strictly speaking, only relevant for the circumstances under which it is measured. A reading that is truly representative of the average pressure is difficult to obtain because of the great variability of pressure in any person. The use to which BP readings are put should be defined, whether for characterizing populations, assessing antihypertensive agents, or managing individual patients. The limitations of any technique must be taken into account. Intra-arterial measurement of BP is the most accurate method, capable of giving a continuous picture. Indirect recordings give a rough estimate of intra-arterial pressure but less information about the relationship between individual subjects and their environment. Ambulatory indirect BP recordings with automated devices compare favorably in accuracy with conventional sphygmomanometers but contain more accurate characterization of an individual's BP during normal daily activities. The ultimate choice of method depends on what information is required in the particular circumstances.