People with CF often have lung infections that occur repeatedly or worsen over time. The lung infections are often caused by PA. Treatment with antibiotics is used to reduce the presence of the bacteria. The antibiotics may be given orally, intravenously, or inhaled as a mist. The purpose of this study was to evaluate whether AZLI, an investigational formulation of the antibiotic aztreonam, is safe in repeated courses in patients with CF and PA.