Nasal and bronchial brushings and bronchial biopsies were evaluated from patients with cystic fibrosis (CF) and from normal subjects to quantify epithelial and inflammatory cell types. Epithelial in both groups were dominated by ciliated cells. The relative proportions of epithelial cells recovered by brushing and biopsy were similar, but with more basal cells from biopsies than from brushings. In nasal brushings, the numbers and percentages of epithelial subtypes were similar in both groups. In bronchial brushings, the number of recovered cells was 2.5-fold increased in the CF group compared with that in the normal group because of large numbers of neutrophils. The proportion of ciliated cells was lower in the CF group than in the normal group. Thus, even though the CF transmembrane conductance regulator mutations are expressed similarly in the nasal and bronchial epithelium in CF, the consequences are different, with little inflammation and no changes in the proportions of epithelial cells in the nasal epithelium, compared with marked neutrophil inflammation on the epithelial surface and significant changes in epithelial populations in the large airways. Airway brushing permits repetitive evaluation of the airway epithelium in CF, a useful methodology in the assessment of new therapies for this disorder.