Some neutrophil products such as elastase, myeloperoxidase (MPO), alkaline phosphatase (ALKP), superoxide (O2.-), and 5-oxo-eicosatetraenoic acid (5-oxo-ETE) may play an essential role in neutrophil mediated lung injury in the course of Bovine Respiratory Disease (BRD). The aim of this study was to evaluate how this neutrophil secretory action correlates with the severity of clinical signs on the basis of clinical score. Neutrophils isolated from 60 BRD heifers and from 30 healthy heifers were cultured, and then elastase, MPO, ALKP superoxide, and 5-oxo-ETE production were assessed. These studies revealed that the correlation between neutrophil secretory action and clinical signs exist. The clinical score correlated highly (r = 0.65) with elastase release, it correlated moderately with ALKP (r = 0.44), and correlated weakly with MPO (r = 0.28), 5-okso-ETE (r = 0.29), and superoxide anion (r = 0.3). The strongest relation was observed between elastase release and severity of clinical signs.