Given the ubiquitous distribution of catecholamines in mammals, and their importance in a range of physiological processes pivotal to blood pressure regulation, the subject of catecholamines and essential hypertension has a broader context than simply consideration of sympathetic nervous system and adrenal medullary dysfunction. These further matters are the likely involvement in hypertension pathogenesis of the CNS catecholaminergic neurones influencing peripheral sympathetic outflow, the possible pathogenetic significance of adrenaline released as a cotransmitter in sympathetic nerves, and the natriuretic renal tubular dopamine mechanisms for regulating body sodium balance which appear to be impaired in patients with essential hypertension. The central consideration, however, remains the important issue of the causes and consequences of the now well-documented sympathetic nervous overactivity which characterizes the early developmental phases of essential hypertension.