Arguing against evaluating patients for undiagnosed OSA is the absence of evidence that treatment improves stroke-related outcomes, including recurrence. Since the last version of this guideline, a trial of 2717 patients with moderate to severe OSA and coronary or cerebrovascular disease failed to show a benefit of CPAP on recurrent vascular events.303 In favor of evaluating stroke patients is the high prevalence of undiagnosed OSA, combined with evidence that treatment improves daytime sleepi- ness, BP, sleep-related quality of life, and physi- If an evaluation is undertaken, options include questionnaires to identify patients at high risk for OSA who can be selectively referred However, available questionnaires show inconsistent performance in patients with stroke.332 In addition, the prevalence of OSA after stroke is sufficiently high to justify omitting prescreening before polysomnography when detection of asymptomatic OSA is clinically warranted. Facility-based (ie, sleep laboratory based), multichannel polysomnography is the ref- erence standard for diagnosing OSA. Home (ie, out of sleep laboratory) monitors are appropriate in selected patients.316,317 Although the American Academy of Sleep Medicine recommends against the use of home testing in patients with stroke,334 recent research suggests that home testing can be Knowledge Gaps and Future Research Observational data show a high prevalence of OSA among patients with acute ischemic stroke, and small trials suggest that treatment may improve several important outcomes. Together, this considerable vol- ume of data support the hypothesis that early detec- tion and treatment of OSA may be helpful for selected patients. Proving this hypothesis will require adequately designed clinical trials. Such trials will need to consider the following: The selection of patients who might benefit from CPAP, Timing of testing and treatment in relation to stroke onset, Type of testing (in home or in facility), and Dose/type of CPAP. 