Patients with Cystic Fibrosis have multiple pulmonary infections and repeated antibiotic treatment. These factors taken together with high sputum viscosity and slow motility of the gastrointestinal tract-may change the pathogenicity and consistency of the intestinal pathogens. Part of the pulmonary infections in CF patients are due to intestinal pathogens. A pilot study performed by the researchers using probiotics in CF patients showed a decrease in the rate of pulmonary infections. Therefore,we planned a double-blind placebo-controlled trial to examine the effect of probiotics on pulmonary infections, sputum bacteria and sputum inflammatory markers in CF patients.