The majority of cystic fibrosis (CF) patients die from a progressive pulmonary disease.Airway inflammation plays a major role for the pathogenesis of CF lung disease, and ultimately leads to lung destruction. The release of oxidants during the inflammation process leads to a chronic imbalance of oxidants and antioxidants and may be a central component leading to irreversible lung damage in CF patients. The antioxidant glutathione, which is a naturally occurring tripeptide, is depleted in the extracellular epithelial lining fluid of the CF lung. The elevation of reduced level to normal and also the augmentation of glutathione concentrations above the normal level, as observed in smokers and during defence of Pseudomonas infection, may be desirable to avoid lung damage. Data from pilot studies in humans and animals have indicated that the glutathione concentrations in epithelial lining fluid can be elevated by aerosol application.