Experimental hypertensions following sino-aortic deafferentation or manoeuvres not involving initially the baroreceptor reflexes are discussed in relation with a simple graphical analysis of these reflexes. Blood pressure increases only slightly as a result of interruption of the sino-aortic afferences, but its variability is markedly enhanced. On the other hand, the final level of arterial pressure in various forms and non-neurogenic hypertension appears independent from the presence of the baroreceptor reflexes ("resetting"). Thus, the baroreceptor reflexes are of primary importance in limiting variations around a given level of arterial pressure, but they do not really set this level since it can be modified easily by other blood pressure control systems. In order to emphasize the role of the baroreflex in the short-term regulation of blood pressure and other haemodynamic variables, its significance in "whole-body autoregulation" and in the cardiovascular effects of vasopressin is discussed.