Obstructive sleep apnoea (OSA) is a form of sleep disordered breathing with a high prevalence rate and is often underdiagnosed. OSA is associated with hypertension, coronary artery disease, stroke, peripheral vascular disease, heart failure, and arrhythmias. The presence of OSA may be a strong predictor of fatal cardiovascular events in patients with cardiovascular disease (CVD). Increased sympathetic drive, activation of metabolic and inflammatory markers, and impaired vascular function are some of the proposed mechanisms that could explain the association between OSA and cardiovascular diseases. Understanding these mechanisms is important for identifying treatment strategies. The presence of OSA should be considered in clinical practice, especially in patients with CVD. Randomized intervention studies are needed to establish whether early identification and treatment of OSA patients reduces cardiovascular morbidity.