Previous work has shown an increase in CD8+ T-cells, neutrophils and eosinophils in small airway subepithelium in smokers. The authors have now investigated whether similar changes occur in the large airways. Immunohistochemistry on frozen sections of bronchial biopsies were obtained at bronchoscopy in 11 nonsmokers, eight asymptomatic smokers and 11 smokers with chronic bronchitis and chronic obstructive pulmonary disease (COPD). There was an increase in the number of CD8+ cells infiltrating the bronchial subepithelium in the COPD group compared to the asymptomatic smokers (305 (109-400) versus 92 (41-550) cells x mm(-2), p=0.030). There was a negative correlation between the number of CD8+ cells and the forced expiratory volume in one second (FEV1) %predicted (p=0.005, r=-0.62), and a positive correlation between the number of CD8+ cells and the number of pack years smoked (p=0.017, r=0.42). There was a negative correlation between the activated/total eosinophils ratio and the FEV1 % pred (p=0.017, r=-0.51). There was a negative correlation between pack years smoked and the number of neutrophils (p=0.022, r=-0.36). Smokers who develop chronic obstructive pulmonary disease have increased numbers of CD8+ T-cells in large airways when compared to asymptomatic smokers. Airway obstruction was associated with an increase in the proportion of eosinophils that were activated.