Although atrial fibrillation remains the most common cardiac arrhythmia, the treatment and disposition remain varied. An accept-able standard of practice requires an evidence-based approach. This approach has revealed that half of the patients who present with acute atrial fibrillation will convert to sinus rhythm without intervention. In the hemodynamically stable subset, ascertaining the on-set of atrial fibrillation within 48 hours is critical because this period dictates when and if anticoagulation should be instituted and if and where electrical or chemical cardioversion needs be performed. The hemodynamically unstable patient, however, requires emergent cardioversion, irrespective of the chronicity of atrial fibrillation. An evidence-based approach may serve to optimize treatment and obviate the need for unnecessary hospital admissions.