Bacterial adhesion is probably a prerequisite for colonization of mucous membranes, but adhesion to the bronchial mucosa has not been studied in detail. We investigated adhesion of respiratory pathogens to bronchial epithelial cells, and asked whether chronic bronchitis had an influence on bacterial adhesion. Oropharyngeal and bronchial cells were collected during bronchoscopy from 14 healthy nonsmokers, 22 smokers with nonobstructive chronic bronchitis, and 19 smokers with chronic bronchitis and chronic obstructive pulmonary disease (COPD). Patients with a forced expiratory volume in one second (FEV1) less than 50% predicted were excluded. Adhesion of highly adherent test strains of H. influenzae and S. pneumoniae to these cells were studied. The test strains of H. influenzae and S. pneumoniae were found to adhere well to both oropharyngeal and bronchial cells. H. influenzae showed a higher degree of adhesion both to ciliated and goblet cells from the patients with nonobstructive bronchitis than to cells from the healthy nonsmokers. No corresponding difference was found for S. pneumoniae. The patients with COPD did not differ from the controls in their adhesion values. Our results indicate that bacterial adhesion is of importance for the colonization and retention of H. influenzae in the human airways. For S. pneumoniae the role of adhesion is more uncertain.