Hypertension is the most powerful risk factor for stroke. Blood pressures (BP) measured out of clinic, such as self-measured BP at home and ambulatory BP are the better predictor of stroke than clinic BP. As well as higher 24-hr BP level, disruption of diurnal BP variation is also associated with increased risk for stroke. Recent prospective studies clearly demonstrated that the riser pattern with higher nocturnal BP than daytime BP and nocturnal hypertension per se are closely associated with cardiovascular death and cardiovascular events such as stroke and cardiac disease. The following pathological conditions are closely associated with this riser and non-dipper patter: increased circulating blood volume such as chronic kidney disease and congestive heart failure, autonomic nervous dysfunction such as diabetes particularly with neuropathy, and poor sleep quality such as sleep apnea syndrome. We have developed nocturnal hypoxia-triggered BP monitoring, and have detected marked midnight BP surges at the time of sleep apnea episodes. As the cardiovascular risk is increased in a sleep period in patients with obstructive sleep apnea, this surge may trigger the sleep-onset stroke. Considering that morning BP surge is the risk of stroke in a general population, the time of BP surge may be the time of increased cardiovascular risk. The perfect 24-hr BP control with diminishing exaggerated BP surge may achieve more effective prevention in stroke in hypertensive patients.