Azithromycin is very effective at reducing exacerbations in COPD, but we do not understand the biological mechanism, i.e. anitbiotic effect versus antiinflammatory effect. Because we do not understand how it works (and because of the potential for side effects), azithromycin is not yet widely used. Clinical studies designed to answer this question would help us refine our therapeutic approach and may allow us to minimze side efects in the future by focusing on the anti-inflammatory or anti-bacterial effects. These clinical studies are unlikely to be done by industry.