The observation that mucoid Sp were isolated from the sputum of CF patients more frequently than from patients without CF [Coats et al. in preparation] prompted the question of whether mice with a CFTR defect are more susceptible to infection with highly mucoid Sp compared to their congenic WT littermates since other mucoid bacteria, most notably Pseudomonas aeruginosa (Pa), are associated with progression of CF lung disease [9, 14–19, 29–31]. This evidence concerns the gene CFTR and lung disorder.