A randomized clinical trial evaluated whether azithromycin improves pulmonary function in patients with cystic fibrosis infected with Pseudomonas aeruginosa. Patients received either azithromycin 250 mg PO or placebo 3 days per week (Mon, Wed, Fri) for 168 days. At the end of the study, those receiving azithromycin showed greater improvements in FEV1 and had a decrease in pulmonary exacerbations. The azithromycin patient group also weighed an average of kg more than placebo patients which suggests an improvement in nutritional status. The results of this study are consistent with 2 other studies suggesting benefits of azithromycin in CF patients.