Blood pressure is a variable parameter for which the isolated determination cannot be considered as a characteristic of the subject. Therefore, the clinical measurement of blood pressure constitutes the method of reference but presents limits and causes of errors which pose a problem for its validity in evaluating the average blood pressure level in certain patients. In order to overcome the limits of occasional measurement, different methods of blood pressure measurement have been proposed. Among these methods, self monitoring of blood pressure by the patient and 24 hour ambulatory blood pressure monitoring (ABPM) are the most used. Each of these methods presents advantages and disadvantages, indications and limits of use. The information obtained by each of them is of a different nature: these methods are not substitutes but are complementary. Self monitoring and ABPM seem to evaluate the pressure load better than clinical monitoring and are better correlated to the organic effects of hypertension and thus the cardiovascular morbidity and mortality, ABPM in particular. However, it remains to be clarified whether the use of these methods in the evaluation of cardiovascular risk and the therapeutic management of the hypertensive can improve the long term cardiovascular prognosis.