The aim of our study was to determine the frequency of microbiological culturing and prevalence of colonization by principal pathogens of the respiratory tract of Italian cystic fibrosis patients. Data on all Italian cystic fibrosis patients were collected using a questionnaire sent to all Italian CF Centers. Results were obtained of microbiological cultures from 2,521 patients. Information was gained regarding the method of gathering biological samples, the percentage of patients undergoing microbiological culturing regularly, the procedures used to isolate bacteria and types of culture media used which were selective for Burkholderia cepacia. Ninety-four percent of Italian CF patients are regularly tested microbiologically. Sputum and pharyngeal cultures are most often carried out. 49% of Italian patients are colonized by Staphylococcus aureus, 5.4% by Haemophilus influenzae, 48.9% by Pseudomonas aeruginosa and 3.8% by Burkholderia cepacia. In Italy there is a high prevalence of CF patients colonized by Staphylococcus aureus and a low prevalence of patients colonized by Haemophilus influenzae. The prevalence of Burkholderia cepacia and Pseudomonas aeruginosa does not differe significantly from other countries examined.