Exacerbations are a characteristic feature of chronic obstructive pulmonary disease and contribute significantly to associated morbidity and mortality. Renewed interest in this common clinical problem and research using new investigative tools has enhanced substantially the understanding of the pathogenesis of exacerbations. Results of recent clinical trials and observational studies have allowed refinements in treatment of exacerbations that should im-prove patient outcomes. This article discusses a rational, stratified approach to the use of antibiotics for this condition based on these recent studies.