To investigate the effect of smoking cessation on the airway inflammatory process present in nonatopic subjects with chronic bronchitis, we obtained bronchial biopsies from nine current smokers and seven exsmokers, all with symptoms of chronic bronchitis at the time of the study, and from seven healthy nonsmoking subjects. The exsmokers had stopped smoking on average 13 yr before the study, yet cough and production of sputum had persisted. Bronchial biopsies were assessed using immunohistochemical techniques to investigate the number of inflammatory cells, the markers of mononuclear cell activation, and the expression of endothelial adhesion molecules and cytokines in the subepithelium. Current smokers and exsmokers had an increased number of macrophages, IL-2R-positive cells, VLA-1-positive cells, ICAM-1-positive vessels, and E-selectin-positive vessels compared with normal nonsmoking subjects, but the number of cells positive for neutrophils, EG-2, CD3, CD4, CD8, TNF-alpha and IL-1 beta were similar among the three groups. No differences were observed between current smokers and exsmokers for any parameter examined. In conclusion, the inflammatory process present in the airway mucosa of current smokers may persist after smoking cessation in subjects who continue to have symptoms of chronic bronchitis.