Data collected in experimental animals and in humans support the hypothesis that sympathetic neural mechanisms are involved in the development and progression of hypertension. Direct approaches to assess human adrenergic cardiovascular drive have shown that sympathetic activation occurs in hypertensive patients, the magnitude of which is proportional to the degree of elevation of the blood pressure. Evidence has also been obtained that sympathetic activation participates in the development of hypertension-related target organ damage, such as left ventricular diastolic dysfunction, left ventricular hypertrophy and arterial remodelling and hypertrophy. Despite the large amount of information collected on the main features of the hypertension-related neurogenic abnormality, the causes of the sympathetic activation remain undefined, although alterations in the reflex modulation of adrenergic drive and/or participation of metabolic factors are likely candidates. This paper will provide background information on the behaviour of the sympathetic nervous system in experimental hypertension, followed by a review of the main features, mechanisms and effects of the sympathetic overdrive in human hypertension. Finally, the new frontiers of research in the area of therapeutic intervention aimed at reducing the adrenergic overdrive will be highlighted.