Alterations in transepithelial ion fluxes are a primary pathophysiologic feature in cystic fibrosis (CF). Chronic respiratory infections and host responses are secondary aggravating pulmonary complications of this disease. In the present study, the application of the freeze-fracture technique to samples of nasal and tracheal epithelium from patients with CF has provided a perspective of large areas of cell membrane for the evaluation of possible structural correlates to the pathophysiology of this disease. A variety of aberrant configurations in stranding pattern and disorganization of the epithelial tight junctional complexes in CF airway epithelium are described. Additionally, examination of ciliary membranes revealed the presence of compound cilia and dysmorphology of ciliary necklace configuration. These features are thought to represent acquired structural lesions possibly derived from chronic infection and/or host responses which may further exacerbate abnormal ion transport properties and decrements of ciliary function that appear to be associated with the airway epithelium of individuals with CF.