Objectives: The purpose of this study was to analyze the effect of beta blockade on outcome in patients with heart failure (HF) and atrial fibrillation (AF). Background: Beta-blockers are widely used in patients with HF and AF. Recommendation in current HF guidelines, however, is based on populations in which the most patients had sinus rhythm. Whether beta-blockers are as useful in AF is uncertain. Methods: Studies were included that investigated the effect of placebo-controlled, randomized beta-blocker therapy in patients with AF at baseline and HF with reduced systolic left ventricular ejection fraction (LVEF)