Background: Data regarding the stroke risk in patients with heart failure with normal ejection fraction (HFNEF) and nonvalvular atrial fibrillation (AF) who are not treated with anticoagulation is limited. Methods: Clinical and echocardiographic data from Feb. 2008 to Jul. 2008 in patients with nonvalvular AF who were not treated with anticoagulation were investigated. Patients with left ventricular ejection fraction ���50%, severe valvular or pericardial disease, recent stroke or transient ischemic attack (TIA), recent acute coronary syndrome or revascularization, severe pulmonary disease, or malignancy were not involved in the analysis. Of the 207 patients, 151 patients had nonvalvular AF without heart failure (HF) and 56 patients were diagnosed as nonvalvular AF with HFNEF. We compared the rate of ischemic stroke, death, and composite of ischemic stroke and death between two groups. Results: Patients with HFNEF were older than those without HF (71.9 vs. 63.6 years, P<0.001). Female sex, hypertension, chronic kidney disease, angina, and use of beta blocker were more common in patients with HFNEF. With a median follow-up of 2.8 years, the rate of ischemic stroke was significantly higher in patients with HFNEF than those without HF (21.3% vs. 9.3% at 3 years for AF with HFNEF vs. AF only; P=0.035, Fig. 1A). Although the univariate analysis showed no significant difference in the rate of death between two groups, it tended to be higher in patients with HFNEF (11.0% vs. 1.7% at 3 years; P=0.060, Fig. 1B). The rate of composite of ischemic stroke and death was higher in patients with HFNEF than those without HF (27.5% vs. 10.1% at 3 years; P=0.006, Fig. 1C). After adjustment for previous stroke or TIA, and no use of aspirin, the risk of ischemic stroke was consistently higher in patients with HFNEF (hazard ratio, 2.79; 95% confidence interval, 1.09 to 7.13; P=0.032) Conclusion: HFNEF is associated with the increased risk of stroke in patients with nonvalvular AF who are not treated with anticoagulation.