Cystic fibrosis (CF) is the most common genetic disorder amongst Caucasians and is associated with pulmonary infection and respiratory failure leading to a shortened life expectancy. Chronic respiratory infection by PseudomonaTaeruginosa contributes significantly to the morbidity and mortality associated with CF. hi the UK, I number of transmissible strains have been identified, the most common of which is the Liverpool Epidemic Strain (LES) of P. aeruginosa, which has been associated with causing greater morbidity of CF patients, superinfection, and the infection of non-CF parents of a CF patient. The aim of this project was to identify some of the characteristics of this successful strain and determine the factors that contribute to its success.