Abstract: Syndrome Z is defined as the co-occurrence of obstructive sleep apnea (OSA) and metabolic syndrome. There is a paucity of information on the magnitude of syndrome Z in the community and the factors associated with it. Obstructive sleep apnea (OSA) has been linked to increased cardiovascular morbidity and mortality from both coronary heart disease and stroke [1-3] but whether this risk is due to coexistent known cardiovascular risk factors or specific effects of OSA remains to be established. In populations at risk of vascular disease, many patients who experience a cardiovascular event either do not have identifiable risk factors or have disease severity which appears to be out of proportion to their known risk factors. A lot of the variance in the incidence of vascular disease is therefore not explained by known risk factors. It is possible that OSA is a cardiovascular risk factor, previously largely unrecognized, which may account for some of the apparently unexplained variance in vascular risk. Systemic hypertension during daytime measurements of blood pressure is common in patients with OSA [8] but a causal link between these two conditions has been disputed [2, 3]. Sleep apnea has been shown to be common in patients with hypertension [8-11] and, conversely, patients with OSA have a high prevalence of hypertension [1, 5]. The frequency with which risk factors for hypertension such as increasing age and obesity coexist in patients with OSA has confounded identification of a causal relationship between OSA and hypertension.