There are evidences that the upper airways (nose, paranasal sinuses) and the oral cavity might be reservoirs of Pseudomonas aeruginosa (Pa) and other bacterial species causing infections in the CF lung. The aim of this project is to evaluate the incidence of potentially pathogenic bacterial species in the nasal/paranasal district in a series of CF patients with and without Pa pulmonary chronic infection; further, to compare the upper district bacterial flora with the flora found in sputum (by biochemical methods and molecular typing). The results will outline if monitoring and eradication of the nasal and oral potentially pathogenic microflora in CF patients may avoid or postpone the emergence of a chronic lung infection.