Abstract: The present invention relates to pharmaceutical kits and methods to treat lung inflammation and redox imbalance in human cystic fibrosis patients using pharmaceutical compositions containing N-acetylcysteine (NAC), pharmaceutically acceptable salts of N-acetylcysteine, or N-acetylcysteine derivatives. In phase I studies, treatment with oral NAC at a dose of from about 1800 mg/day to about 3000 mg/day for a period of 4 weeks produced significant positive effects, namely, it decreased absolute numbers of white blood cells and neutrophils in the sputum and produced concomitant decreases in sputum neutrophil elastase specific activity and sputum interleukin-8 levels, suggesting an amelioration of lung inflammation in the patients. These effects were associated with an increased total GSH level in whole blood as well increased staining for reduced GSH in blood neutrophils, both of which reflect an amelioration of the redox imbalance in the patients.