Background: RE-LY (Randomized Evaluation of Long-term Anticoagulation Therapy) is an international multicenter study (18,113 patients from 967 centers in 44 countries) that demonstrated the ability of dabigatran to reduce the occurrence of both stroke and hemorrhage in patients who had atrial fibrillation (AF) with high risks of stroke compared with patients who received warfarin. From Japan, 326 patients were randomized in RE-LY. Methods and Results: RE-LY was designed to compare 2 fixed doses (110mg or 150mg, twice daily) of dabigatran, each administered in a blinded manner, with open-label use of warfarin. There were no major differences in patient demographic information among the overall study population and Japanese patients. However, in Japanese patients, the proportion of prior stroke was higher but prior myocardial infarction was lower than in the overall. The yearly rate for the primary endpoints (stroke and systemic embolism) was 1.38, 0.67 and 2.65%/year for 110mg and 150mg dabigatran twice daily and warfarin, respectively. These results were similar to the overall results (1.54, 1.11 and 1.71%/year for each group, respectively). For any bleeding, the relative risk of dabigatran at 110mg and 150mg twice daily over warfarin was 0.79 and 1.06, respectively, which was similar to the findings overall (dabigatran 110mg twice daily: 0.78; 150mg twice daily: 0.91). Conclusions: In RE-LY, the efficacy and safety profiles of dabigatran for Japanese AF patients at high risk of stroke were essentially the same as for the study population overall. (Circ J 2011; 75: 800 - 805)