Background and Purpose- China bears a heavy burden of stroke because of its large population of elderly people and the propensity for stroke. Previous studies have examined the association between air pollution and stroke mortality or hospital admission. However, the global evidence for adverse effects of air pollution on survival after stroke is scarce. Methods- We used the first national hospital-based prospective registry cohort of stroke in China, which included 12 291 ischemic stroke patients who visited hospitals during 2007 to 2008. All patients were followed for 1-year poststroke. Deaths during the follow-up period were recorded. Participants' 3-year prestroke exposures to ambient PM1, PM2.5, PM10 (particulate matter with aerodynamic diameters