The CHADS2 and CHA2DS2-VASc scores, that is, ischemic stroke risk indices for patients having atrial fibrillation (AF), may also be useful as bleeding risk indices. Japanese patients with AF, who routinely took oral antithrombotic agents were enrolled from a prospective, multicenter study. The CHADS2 and CHA2DS2-VASc scores were assessed based on information at entry. Scores of 0, 1 and ⩾2 were defined as the low, intermediate and high ischemic risk categories, respectively, for each index. Of 1221 patients, 873 took warfarin, 114 took antiplatelet agents and 234 took both. The annual incidence of ischemic stroke was 0.76% in the low-risk category, 1.46% in the intermediate-risk category and 2.90% in the high-risk category by CHADS2 scores, and 1.44, 0.42 and 2.50%, respectively, by CHA2DS2-VASc scores. The annual incidence of major bleeding in each category was 1.52, 2.19 and 2.25% by CHADS2, and 1.44, 1.69 and 2.24% by CHA2DS2-VASc. After multivariate adjustment, the CHADS2 was associated with ischemia (odds ratio 1.76, 95% confidence interval 1.03-3.38 per 1-category increase) and the CHA2DS2-VASc tended to be associated with ischemia (2.18, 0.89-8.43). On the other hand, associations of the indices with bleeding were weak. In conclusion, bleeding risk increased gradually as the CHADS2 and CHA2DS2-VASc scores increased in Japanese antithrombotic users, although the statistical impact was rather weak compared with their predictive power for ischemic stroke.