The study investigated the relationship between apoptosis of peripheral blood neutrophils during exacerbation of chronic obstructive pulmonary disease (COPD) and the inflammatory response that characterises this condition. Twenty-six hospitalised patients with COPD exacerbation and 13 controls were included. Three sequential blood and sputum samples were obtained from patients at admission, after 3 days and at discharge. Blood apoptotic neutrophils were measured by flow-cytometry and light microscopy. Serum and sputum levels of IL-6, IL-8 and TNF-alpha were determined by an immunoassay technique. We found a significantly reduced percentage of apoptotic neutrophils at the onset of COPD exacerbation which increased over time (1.1+/-0.4% at admission vs. 2.4+/-0.4% at discharge, P<0.0001). Patients presented no changes in serum cytokines neither during exacerbation nor in comparison to controls. In contrast, sputum levels of cytokines were significantly increased compared to serum levels. There was no significant correlation between the apoptotic neutrophils and the cytokine concentrations in serum or sputum. None of the clinical parameters, such as smoking, microbial infection, corticosteroids or hypoxemia showed a correlation with neutrophil apoptosis. No relationship could be found between the reduced percentage of apoptotic neutrophils in blood and serum concentration of IL-6, IL-8 and TNF-alpha or other clinical parameters in patients with COPD exacerbation.