BACKGROUND There are strictly determined conditions under which blood pressure measurement should be done and diagnosis of hypertension made. The first BP measurement should be performed on both arms. If there is a difference, controls should be made on the side on which the pressure is higher. In older persons the Osler manoeuvre should be made in order to exclude pseudohypertension. One should be aware that in hospitalized patients the BP is lower due to the bed rest itself. SELF-MEASUREMENT OF BLOOD PRESSURE: It seems that erroneous interpretation of blood pressure fluctuation and the tendency for self-medication by patients are the most important shortcomings of blood pressure self-monitoring. According to the World Hypertension League instructions, the BP self-measurement is not recommended for patients obsessed by the disease, neurotic and anxious persons, old subjects and in those who are physically handicapped. Since the diagnosis of hypertension should be made by the physician in office conditions, in our opinion the evolution of the disease and effects of treatment should be estimated under the same conditions. Ambulatory 24-hour monitoring is of a considerable diagnostic, therapeutic and prognostic importance over the casual or self-measurement, but one should be familiar with some peculiarrities of this method. Due to the adaptation to the device, the values of BP on the first measurement, particularly during the first 5 hours are significantly higher than during the subsequent measurements. In some subjects the values during the night may be higher due to the sleeping disturbances caused by the procedure. Differentiation between dippers and non-dippers has some prognostic and therapeutic implications. White coat hypertension may be successfully established by the ambulatory measurement. There is also a correlation between the BP variations and the myocardial mass. The trough:peak ratio may contribute to the estimation of efficiency of a certain drug. There are particular indications for ambulatory BP monitoring: the differences between the office and home values of BP are considerable; borderline hypertension; hypertension without signs of the target-organ damage; transitory hypertension of hypotension; syncopal attacks; vague symptoms in hypertensive patients; atypical or nocturnal angina; evaluation of the efficiency and duration of drug action; for research purposes.