Acute diseases and chronic conditions might be associated with altered blood neutrophil functions. The aim of this study was to investigate teh effects of stable chronic obstructive pulmonary disease (COPD) and superimposed acute bacterial bronchopneumonia (ABP) on the phagocytosis and oxidative metabolism of blood phagocytes. The 129 participants were assigned to 6 groups: group 1, healthy controls; group 2, previously healthy controls with ABP; group 3, patients with stable COPD on inhaled corticosteroids (IC); group 4, individuals with stable COPD on IC and ABP; group 5, patients with stable COPD requiring oral corticosteroids (OC); group 6, individuals with COPD on OC and ABP. Phagocytosis and oxidative burst was measured. Both tests showed a significant difference between the groups without acute infection when compared to the patients with ABP. No differences were observed between patients with stable COPD without ABP (groups 3 and 5) and group 1. The number of phagocytized E. coli/cell was 9.1 +/- 0.37, 7.9 +/- 0.27 and 8 .2 +/- 0.28 (groups 2, 4, and 6, respectively) reversed the observed changes. We conclude, that acute bacterial bronchopneumonia is associated with an impairment of phagocytosis and oxidative metabolism in blood. We suggest, that stable COPD has no influence on phagocytosis and oxidative burst.