Background and Purpose-Sleep-disordered breathing (SDB) is frequent in stroke patients. Risk factors, treatment response, short-term and long-term outcome of SDB in stroke patients are poorly known. Methods-We prospectively studied 152 patients (mean age 56Ϯ13 years) with acute ischemic stroke. Cardiovascular risk factors, Epworth sleepiness score (ESS), stroke severity/etiology, and time of stroke onset were assessed. The apnea-hypopnea index (AHI) was determined 3Ϯ2 days after stroke onset and 6 months later (subacute phase). Continuous positive airway pressure (CPAP) treatment was started acutely in patients with SDB (AHI Ն15 or AHI Ն10ϩESS Ͼ10). CPAP compliance, incidence of vascular events, and stroke outcome were assessed 60Ϯ16 months later (chronic phase). Results-Initial AHI was 18Ϯ16 (Ն10 in 58%, Ն30 in 17% of patients) and decreased in the subacute phase (PϽ0.001).Age, diabetes, and nighttime stroke onset were independent predictors of AHI (r 2 ϭ0.34). In patients with AHI Ն30, age, male gender, body mass index, diabetes, hypertension, coronary heart disease, ESS, and macroangiopathic etiology of stroke were significantly higher/more common than in patients with AHI Ͻ10. Long-term incidence of vascular events and stroke outcome were similar in both groups. CPAP was started in 51% and continued chronically in 15% of SDB pts. Long-term stroke mortality was associated with initial AHI, age, hypertension, diabetes, and coronary heart disease. Conclusions-SDB is common particularly in elderly stroke male patients with diabetes, nighttime stroke onset, and macroangiopathy as cause of stroke; it improves after the acute phase, is associated with an increased poststroke mortality, and can be treated with CPAP in a small percentage of patients. (Stroke. 2006;37:967-972.)