 CF patients often have lung infections that occur repeatedly or worsen over time. The lung infections are often caused by a bacteria called Pseudomonas aeruginosa PA. Treatment with antibiotics can stop or slow down the growth of the bacteria. The antibiotics may be given by mouth, intravenously IV, or by inhalation as a mist. The purpose of this study was to evaluate the safety and efficacy of AZLI, an investigational formulation of the antibiotic aztreonam and administered TID using the PARI eFlow electronic nebulizer, in CF patients with PA. 