In patients with tracheostomy and lacking or non-patent larynx the nose has no longer any climatic function for the lower airways. The comparison of mucosal alterations in the tracheobronchial tree of 5 laryngectomized patients, 5 tracheostomized patients without chronic bronchitis prior to the operation, and 5 otherwise healthy persons, who served as a control group, allows conclusions on the protective function of the intact upper airways. The specimens obtained from the right upper lobe bronchus, the main carina, the middle third of the trachea and below the stoma are examined by means of a scanning electron microscope (SEM). The percentage of the ciliated components of the epithelium is evaluated with a semi-automatically functioning image analyser. In healthy subjects the ciliated cells are clearly reduced close to the main carina. After laryngectomy a reduction of cilia along the entire tracheobronchial tree is observed, whereas at the main carina they are more or less lacking. In patients without preexisting chronic bronchitis the ciliary carpet is also almost totally absent near the carina and the stoma, while it is qualitatively better in the right upper lobe bronchus and the middle trachea. The method presented here, with evaluation of the distribution and ciliary surface morphology, allows quantification of the tracheobronchial mucosal condition under various anatomical and clinical circumstances. If the protective function of the upper airways is missing, the alterations of the tracheobronchial mucosa depend on the extent of the preexisting damage and on the level where the specimen is taken.