Atrial fibrillation (AF), classified as nonvalvular (NVAF) in the absence of rheumatic mitral stenosis or valvular prosthesis,is the most common arrhythmia, with an estimated prevalence of 1.5-2%. AF is associated with a greater risk of arterial thromboembolic events, especially cerebrovascular, whose incidence is 5-7 times higher. The risk of death is also doubled, and AF has a greater degree of disability and probability of recurrence than stroke due to other causes. To prevent stroke in patients with NVAF, antithrombotic treatments are employed with oral anticoagulants such as vitamin K antagonists (VKA) and, in a number of circumstances, antiplatelet agents. Although VKA (mainly warfarin) are highly effective to reduce the risk of stroke, and have been the sole choice for stroke prevention during the last 50 years, their use is limited for a number of reasons: narrow therapeutic range, drug and food interactions, need for monitoring, and risk of bleeding. Recently, new oral anticoagulants (NOACs) have been marketed for this indication. The aim of this study was to determine the standard clinical practice followed in the treatment to prevent stroke in patients with NVAF in Turkey. The purpose of this study is to demonstrate the current status of the clinical background of AF patients and to follow, analyze and evaluate patients with AF in a large multicenter nation-wide trial. The primary inclusion criteria will be age ≥18 years and with electrocardiographically confirmed NVAF (eg, by electrocardiogram, Holter monitoring, etc). The enrollment of patients will be started in February 2014. All the participating institutions will enroll all consecutive patients with NVAF under regular outpatient care or under admission.