Cigarette smoking is the most important cause of chronic obstructive pulmonary disease (COPD). Although the precise sequence of events that leads a smoker to experience airway obstruction is not completely clear, airway inflammation is a relevant factor. To investigate airway inflammation, 12 nonatopic smoking COPD patients with a forced expiratory volume in one second (FEV1) < or = 75% predicted and 10 normal nonsmoking subjects (NS) were studied with bronchoscopy and bronchial lavage (BL). Serum immunoglobulin (Ig)E levels of COPD patients correlated with the smoking history (r=0.7, p=0.008). In BL of COPD patients there was an increase of neutrophils (median, range) (COPD 62.6x10(3), 1.2-323, NS 1.35, 0-19.2, p=0.001), eosinophils (COPD 1.6, 0-6.9, NS 0.15, 0-3.7, p=0.035), the levels of interleukin (IL)-8 (COPD 1079 pg x mL(-1), 121-2,500, NS 20.4, 7.2-59, p=0.001), myeloperoxidase (MPO) (COPD 752 microg x L(-1), 11-5,500, NS 22.1, 8-70, p=0.001) and eosinophil cationic protein (ECP) (COPD 21.5 microg x L(-1), 1.8-161, NS 2, 1.8-4.9, p=0.001). Significant correlations were found in BL of COPD patients between IL-8 and neutrophils (p=0.02), MPO and neutrophils (p=0.02), IL-8 and MPO (p=0.0001) and ECP and eosinophils (p=0.02). In addition, the ratios between the BL levels of MPO and the number of neutrophils and between ECP levels and eosinophils were higher in COPD patients than in NS (p=0.03 and 0.01, respectively). These data suggest that cigarette smoke is associated with increased amounts of airway interleukin-8, a chemotactic factor for neutrophils and eosinophils. Recruited neutrophils and eosinophils are activated and they release increased amounts of inflammatory mediators capable of damaging the bronchial tissue.