BACKGROUND: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. It is a cause of stroke, heart failure, and death. Guideline-based treatment can improve outcomes in AF. Unfortunately, adherence to these guidelines is low. Get With The Guidelines is a hospital-based performance initiative, which has been shown to improve adherence over time. Get With The Guidelines-AFIB is a novel quality improvement registry designed to improve adherence to AF guidelines. METHODS AND RESULTS: Hospitals will be recruited by regional American Heart Association staff and key stakeholders. Inpatients or observed patients with AF or atrial flutter will be enrolled. Data collected will include demographic, medical history, and clinical characteristics including laboratory values and treatments. Decision support will guide adherence to achievement and quality measures designed to improve adherence to anticoagulation, heart rate control, safe antiarrhythmic drug use, and patient education and follow-up. Increased adherence to guidelines will be facilitated using rapid-cycle quality improvement, site-specific reporting including national and regional benchmarks and hospital recognition for achievement. Primary analyses will include adherence to American Heart Association/American College of Cardiology performance measures and guidelines. Secondary analyses will include processes of care, risk stratification, treatment of special conditions or populations and use of particular treatment techniques. CONCLUSIONS: AF is common clinical problem with significant morbidity and mortality. Get With The Guidelines-AFIB is a national hospital-based AF quality improvement program designed to increase adherence to evidence-based guidelines for AF.