The availability of new and more active drugs as well as the progress in emergency medicine have made it possible to deal in new ways with the therapy and management of hypertensive crises. The more aggressive character of this treatment leads us to reconsider the risk/benefit ratio also on the basis of changes brought about by the drugs used in the compensatory cardio-vascular equilibria that have become established in the course of the disease, as well as the possibility, that rapid and intensive pressure reductions bring about phenomena of brain hypoxia to the extent of drug syncope and brain damage. After analyzing phenomena of adaptation of brain circulation to the hypertensive disease, the authors discuss risk factors of therapeutic choices in relation to the mechanism of action of the drugs available and used, to different clinical situations and to the patient's age.