The Apixaban Versus Acetylsalicylic Acid to Prevent Strokes in Atrial Fibrillation Patients Who Have Failed orAre Unsuitable for Vitamin K Antagonist Treatment (AVERROES) trial401 compared apixaban 5 mg twice daily with aspirin 81 to 324 mg daily in 5599 subjects with nonvalvular AF unsuitable for warfarin therapy. The Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation compared the same dose of apixaban with adjusted-dose warfarin (target INR, 2 to 3) among 18201 patients with nonvalvular AF. Subjects in each study had at least 1 additional risk factor for stroke (prior stroke or TIA, Meschia et al Guidelines for the Primary Prevention of Stroke 3775 age 75 years, hypertension, diabetes mellitus, heart failure, or peripheral artery disease). A reduced dose of apixaban 2.5 mg twice daily was used in both studies for subjects with at least 2 of the following: 80 years, body mass 60 kg, or serum creatinine 1.5 mg/dL. AVERROES was terminated after a mean follow-up of 1.1 years when an interim analy- sis found apixaban to be markedly superior to aspirin for the prevention of stroke or systemic embolism (1.6%/y versus 3.7%/y; HR, 0.45; 95% CI, 0.32 0.62) with similar rates of major bleeding (1.4%/y versus 1.2%/y). Germane to primary prevention, apixaban was also superior to aspirin in subjects without prior TIA or stroke (HR, 0.51; 95% CI, 0.35 0.74).403 Over a median 1.8 years of follow-up in ARISTOTLE, the primary outcome occurred in 1.27%/y in the apixaban group (analyzed as intention to treat) and 1.60%/y in the warfarin feriority; P=0.01 for superiority). Much of the difference between the groups could be attributed to a reduction in ICH in the apixaban group (0.24%/y versus 0.47%/y); the differ- ences in ischemic or uncertain type of stroke were minimal (0.97%/y versus 1.05%/y). 