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The CHA2DS2-VASc stroke score (congestive heart failure, hypertension, age ≥75 (doubled), diabetes mellitus, prior stroke or transient ischemic attack (doubled), vascular disease, age 65–74, female) is used in most guidelines for risk stratification in atrial fibrillation (AF), but most data for this score have been derived in Western populations. Ethnic differences in stroke risk may be present. Our objective was to investigate risk factors for stroke in AF and application of the CHA2DS2-VASc score in an Asian AF population from Korea.A total of 5855 oral anticoagulant–naive nonvalvular AF patients aged ≥20 years were enrolled from Korea National Health Insurance Service Sample cohort from 2002 to 2008 and were followed up until December 2013.The incidence rates (per 100 person-years) of ischemic stroke were 3.32 in the total population, being 0.23 in low-risk (CHA2DS2-VASc score 0 [male] or 1 [female]) and 4.59 in high-risk patients (CHA2DS2-VASc ≥2). Incidence rates of ischemic stroke or the composite thromboembolism end point showed a clear increase with increasing CHA2DS2-VASc score. On multivariable analysis, significant associations between CHA2DS2-VASc risk factors and ischemic stroke were observed; however, the significance of vascular disease or diabetes mellitus was attenuated after multivariate adjustment, and female sex (hazard ratio, 0.73; 95% confidence interval, 0.64–0.84) had a lower risk of ischemic stroke than males. Patients who were categorized as low risk consistently had an event rate <1% per year.The performance of CHA2DS2-VASc score in Asians is comparable with that in Western populations. The score shows good performance in defining the truly-low-risk AF patients for stroke/thromboembolism.