This document provides clinical recommendations for the prevention of chronic obstructive pulmonary disease (COPD) exacerbations. It represents a collaborative effort between the European Respiratory Society and the American Thoracic Society.Comprehensive evidence syntheses were performed to summarise all available evidence relevant to the Task Force's questions. The evidence was appraised using the Grading of Recommendations, Assessment, Development and Evaluation approach and the results were summarised in evidence profiles. The evidence syntheses were discussed and recommendations formulated by a multidisciplinary Task Force of COPD experts.After considering the balance of desirable (benefits) and undesirable consequences (burden in the form of adverse effects and cost), quality of evidence, feasibility, and acceptability of various interventions, the Task Force made recommendations for mucolytic, long-acting muscarinic antagonist, phosphodiesterase-4 inhibitor (roflumilast) and macrolide therapy, as well as a conditional recommendation against fluoroquinolone therapy. All of the recommendations were conditional, except for a strong recommendation for the use of a long-acting antimuscarinic agent versus a long-acting β2-adrenergic, indicating that there was uncertainty about the balance of desirable and undesirable consequences of the intervention, and that well-informed patients may make different choices regarding whether to have or not have the specific intervention.The guideline summarises the evidence and provides recommendations for pharmacological therapy for the prevention of COPD exacerbations