Macrolide agents have both antibacterial properties as well as various effects on the inflammatory system. In recent years there is growing evidence regarding the favourable effects of macrolides in a range of chronic respiratory conditions. Historically, erythromycin and clarithromycin were found to stabilize pulmonary deterioration in diffuse panbronchiolitis. In cystic fibrosis patients colonized with pseudomonas aeruginosa, long term treatment with azithromycin reduces exacerbations and presents improved lung function. A similar effect on prevention of exacerbations has been demonstrated in noncystic fibrosis bronchiectasis. In patients undergoing lung transplantation, long term azithromycin prevents bronchiolitis obliterans syndrome. In patients with chronic obstructive pulmonary disease (COPD), azithromycin prevents acute exacerbations. Chronic treatment with macrolides is associated with adverse effects including gastrointestinal symptoms, interactions with other drugs and cardiovascular complications. Of the macrolides, azithromycin is associated with the lowest interactions and adverse effects and is also the most investigated.