Atrial fibrillation (AF) is associated with high morbidity and mortality, even despite the use of oral anticoagulation (OAC). Soluble suppression of tumorigenicity-2 (sST2) is a member of the interleukin-1 receptor family [interleukin-1 receptor-like 1 (IL1RL1)], which has been associated with an increased risk of mortality and morbidity in heart failure or acute coronary syndrome. We assessed the predictive value of sST2 levels in an unselected 'real-world' cohort of anticoagulated AF patients.