Central structures involved in the regulation of the circulation include the limbic system, the hypothalamus, the ponto-medullary reticular formation, the nucleus of the solitary tract, the dorsal motor nucleus of the vagal nerve, the nucleus ambiguous and the intermediolateral cell column of the spinal cord. This system is organized to produce not single variables but integrated patterns of response. It is an intriguing fact that most of the above structures are densely innervated by central noradrenaline-containing neurones. Destruction of these neurones by intracerebroventricular injection of the neurotoxin 6-hydroxydopamine prevents the development of various types of experimental hypertension, but has no curative effect on established hypertension. In spontaneously hypertensive rats, a supersensitivity of the dorsomedial hypothalamic nucleus to induce pressor responses appears to be governed by central noradrenaline neurones and seems to be involved in the development of this type of genetic hypertension.