Obstructive sleep apnoea (OSA) is highly prevalent, with recent general population studies indicating that up to 50% of males and 23% of females have moderate or severe sleep disordered breathing (SDB) based on an apnoea-hypopnoea index (AHI) of >15 events·h -1 [1, 2]. OSA is recognised as an independent risk factor for systemic hypertension [3] and a nondipping nocturnal blood pressure profile is particularly likely in patients with OSA [4], even in the absence of significant hypertension. Furthermore, hypertension is increasingly recognised as an important predictor of prevalent OSA and appears to be more predictive than excessive day-time sleepiness in some settings [5]. However, recent evidence also indicates that only moderate-severe OSA (AHI >20 events·h -1 ) constitutes a significant independent risk for hypertension [2] and cluster analysis of sleep clinic populations indicates that particular population subtypes are especially associated with hypertension [6].These recent reports regarding the very high general prevalence of SDB and factors that influence the relationship with hypertension prompt a reassessment of the clinical relevance regarding the association between OSA and hypertension, especially nocturnal hypertension, and the underlying mechanisms that may contribute to the development of a nondipping nocturnal blood pressure profile in OSA patients. This topic is important in the context of the recent SAVE (Sleep Apnea Cardiovascular Endpoints) trial report [7] involving 2717 patients with established cardiovascular disease and moderate or severe OSA associated with minimal sleepiness who were randomised to best usual care with or without added continuous positive airway pressure (CPAP) therapy and followed for up to 7 years. CPAP therapy was not associated with any improvement in cardiac or cerebrovascular outcome, although data on secondary and other end-points in the report indicated a small but significant reduction in diastolic blood pressure. This finding is particularly relevant in the context that the average compliance with CPAP was only 3.3 h and a recent meta-analysis indicates that beneficial effects of CPAP on blood pressure in OSA patients with minimal sleepiness are largely confined to patients using CPAP for >4 h per night [8].