Dabigatran is a direct thrombin inhibitor that has been shown in the RE-LY trial to be either noninferior (110 mg b.i.d) or superior (150 mg b.i.d) to warfarin for the prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation and at least one risk factor for stroke. This article summarizes selected subgroup analyses of the RE-LY trial and their reflections, if any, on clinical guidelines.