Besides their antibiotic effect, C14 and C15 macrolides exhibit immunomodulatory properties which can have therapeutic applications for chronic inflammation of the airways. In vitro studies have demonstrated the anti-inflammatory effects of macrolides: decreased productions of IL-6, IL-8, TNF alpha, chemotactism of polymorphonuclear neutrophils. Cell activity is modified with reduced production of elastase and oxidizing agents. These immunomodulator effects appear to result from an interaction with transcription factors which regulate the expression of cell gens. In addition, they lead to a modified bronchial mucosal secretion and have an action on the biofilm and the pseudomonas pilis. Their clinical activity has been demonstrated in panbronchiolitis and is in favor of use in cystic fibrosis. Use of macrolides should be carefully monitored in the event of bronchectasia, COPD, asthma, or chronic rhinosinusitis.