This review article provides an update on two major issues. First, the most recent evidence supporting the occurrence of an association between obstructive sleep apnoea syndrome, or more generally sleep-disordered breathing, and arterial hypertension in humans is summarized and discussed. This includes an evaluation of both cross-sectional and longitudinal studies. Second, new insights into the mechanisms responsible for the appearance of chronic hypertension in individuals suffering from recurrent nocturnal apnoeic episodes are provided, based both on experimental studies in animals and on clinical studies in humans. The relevance of these data for the clinical management of hypertensive patients with sleep-disordered breathing, and the possibility of obtaining a reduction in blood pressure through the application of nasal continuous positive air pressure, is also addressed.