Cigarette smoking causes an inflammatory process in the central airways, peripheral airways, and lung parenchyma, even in smokers with normal lung function. The characteristics of this inflammatory process differ between smokers who develop chronic airflow limitation (COPD) and those who do not develop chronic airflow limitation: there is an increased infiltration of CD8-positive T lymphocytes in smokers with COPD. We examine whether airway inflammation alters with increasing severity of disease. When the disease becomes severe, a prominent neutrophilia occurs. The precise roles of the CD8(+) T lymphocyte and the neutrophil in the pathogenesis of COPD still remain to be determined. Saetta M. Airway inflammation in chronic obstructive pulmonary disease.