Background Oral anticoagulants (OACs) are recommended for nonvalvular atrial fibrillation (NVAF) patients with moderate-to high-stroke risk. Objective To examine nationally reflective OAC usage in incident NVAF patients longitudinally. Design Three-year retrospective cohort analysis. Setting Medicare Part D recipients in the contiguous United States. PARTICIPANTS:52,465 Medicare beneficiaries with incident NVAF in 2010 with two or more atrial fibrillation diagnoses seven or more days apart. Main outcome measure Stroke risk via congestive heart failure, hypertension, age greater than or equal to 75, diabetes, stroke, vascular disease, age 65-74, sex category (CHA2DS2-VASc) score. Primary outcome was proportion of patients receiving one or more OACs post-NVAF diagnoses. Results Of 48,980 high-risk patients, 32.7% received one or more OAC within 60 days of diagnosis. By close of 2011, 48% had one or more OAC. OAC use increased to 52.9% by close of 2012. Conclusions Fewer than 33% of high-risk NVAF patients received OACs within 60 days of diagnosis in 2010. Despite increased use over time, oral anticoagulation was below 53% at study end. Use of OACs declined with CHA2DS2-VASc greater than 6. Expanded efforts are warranted to augment OAC use in high stroke-risk patients.