Obstructive Sleep Apnea (OSA), defined by shallow breaths or complete cessation of breathing for more than 10s, is a significant contributing factor for the developments of hypertension, myocardial infarction, stroke and neuropsychological impairments. In this study, we have investigated the relation between apnea duration and apnea induced variations in cerebral blood flow velocity (CBFV) concomitant with blood pressure changes in 9 sleep apnea subjects (8 male and 1 female; Age: 46.0±11.6 years; BMI: 34.5±7.8 kg/m(2); AHI: 81.6±41). As apnea duration increased from 10s to greater than 30s, the mean percentage rise in CBFV increased from 22% to 42% for amplitude and 22% to 33% for area respectively. For blood pressure, the values increased from 14% to 26% for amplitude and 14% to 23% for area respectively. The results suggest that the apnea duration has a measurable effect on the degree of rise in both cerebral blood flow velocity and arterial blood pressure during apnea episodes (p=0.0002).