Epidemiological studies have shown a strong association between sleep-disordered breathing (SDB) and cerebrovascular diseases. A total of 114 male patients, aged 40-65 years, referred to sleep laboratory for the evaluation of snoring and disturbed sleep were studied. Subjects were divided into three groups: habitual snoring, mild-moderate and severe obstructive sleep apnea syndrome (OSAS), respectively, determined by using three respiratory disturbance index (RDI) cut points (</=5, 5 < RDI < 30 and >/=30). Measurement of intima-media thickness (IMT) and the presence of plaque were determined by ultrasonographic evaluation. Major vascular risk factors such as hypertension, diabetes, smoking, hyperlipidemia, and obesity were determined. The OSA groups had significantly higher IMT values compared with the habitual snoring group. Three groups were significantly different with regard to the presence of plaque. Age and body mass index were found to be significantly associated with IMT while age and RDI were found to be most probably predictive for plaque. There were no significant differences amongst the three groups with respect to age, prevalence of hypertension and diabetes, smoking, total cholesterol and total triglyceride levels. These findings suggested that SDB is a predisposing factor for the atherosclerotic process and precipitate plaque particularly when associated with higher RDI.