Neutrophilic granulocytes in the lower respiratory tract are of decisive importance for the elimination of pathogenic germs in bacterial pneumonia. On the other hand, the liberation of phagocyte products (e.g. elastase) can result in tissue damage in the parenchyma of the lungs. For this reason, we determined in patients suffering from acute pneumonia (n = 21), in patients with acute pneumonia associated with immunosuppression (n = 12), in patients who had overcome their pneumonia (n = 9) and in controls (n = 17) in bronchoalveolar lavage (BALF) and in plasma, the concentration of the locally produced granulocyte products myeloperoxidase (MPO), lactoferrin (LF) and elastase-alpha 1 proteinase complex (ELA) as well as of the alpha 1 proteinase inhibitor (alpha 1 Pi) and alpha 2 proteinase inhibitor (alpha 2 Pi) via chemoluminescence immunoassay, and compared the same with the differential cell count in the BALF. The protein concentrations were referred to the albumin concentration (Alb) for standardisation. This concentration did not differ significantly between the various patients and control groups. The BALF concentration of ELA in the group with pneumonia (median: 86.3 micrograms/l or 8.5 micrograms/mg Alb) was about eight times higher than in the group of patients suffering from pneumonia with immunosuppression (median: 16 micrograms/l or 1.0 micrograms/l Alb, p less than 0.001) or in whom the pneumonia was no longer present (17.6 micrograms/l or 0.5 micrograms/mg), and approximately 40 times higher than in the control group (3 micrograms/l or 0.2 micrograms/mg, respectively). Similar results were obtained for LF (61 micrograms/mg Alb vs. 11.3; 16.8 and 5.9 micrograms/mg; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)