In the recent years intensive research has revealed numerous negative consequences of obstructive sleep apnea (OSA) for the cardiovascular system. The pathophysiological interaction between OSA and coronary artery disease is complex and comprises neural, humoral, mechanical and haemodynamic components. One of the most important effects of OSA is an increase of sympathetic nerve traffic, which persists during the day and is thought to play a key role in the association of OSA and elevated systemic blood pressure. Nowadays, OSA is accepted as an independent risk factor for arterial hypertension. Several investigations support an association of OSA with ischemic ST-segment changes, ventricular arrhythmias, and sudden cardiac death. In line with this, a growing body of evidence strongly supports OSA having prognostic implications for cardiovascular morbidity and mortality. Continuous positive airway pressure (CPAP) has been shown to have several beneficial effects on the cardiovascular system. Uncontrolled studies indicate that it reduces cardiovascular risk in patients with severe OSA and increased risk or manifest coronary artery disease. However, ongoing studies still have to confirm this.