Obstructive sleep apnea (OSA) syndrome is a highly prevalent disorder affecting 2%-4% of the general population in the United States. Clinical studies have shown that OSA is common among stroke patients, with a prevalence exceeding 50%. The central nervous system during stroke-in-progress or hours poststroke is susceptible to further ischemia and tissue injury due to loss of cerebral autoregulation and tissue hypoxia. The presence of OSA in the setting of stroke is associated with an unfavorable clinical course, including early neurological worsening, delirium, depressed mood, impaired functional capacity and cognition, longer period of hospitalization and rehabilitation, and increased mortality. Several cohort studies have demonstrated that OSA significantly increases the risk of stroke independent of potential confounding risk factors. Randomized controlled trials of continuous positive airway pressure (CPAP) in OSA patients with follow-up of cerebro- and cardiovascular outcomes suggest a clinically significant risk reduction associated with the use of CPAP.