This project (funded by the IWT-TBM program) will organize a randomized placebo-controlled multicenter intervention trial in 500 COPD patients to study the effectiveness and safety of azithromycin therapy in the acute setting of COPD exacerbations requiring hospital admission. Although long-term use of azithromycin is proven effective to prevent exacerbations, inherent risks outweigh the benefits. By reducing the dose and duration of the azithromycin treatment and by restricting the treatment to acute periods with highest risk for treatment failure, benefits may counterbalance potential side effects, which may result in a new treatment strategy for these acute events.