The aim of this study was to determine the prevalence of M. bovis pneumonia in slaughtered cattle in Bursa region, to perform the histopathological investigation of these cases, to demonstrate the agent with bacteriological and immunohistological examination and to characterize the inflammatory response against the agent. A total of 1413 lungs were examined at slaughter houses and 136 lungs (9.63%) with signs of pneumonia were sampled. Ten pneumonic lungs from the department archive were also included in the study. Bacteriological and immunohistochemical examination revealed M. bovis as the cause of pneumonia in 39 animals. In the classification of pneumonia regarding the exudate and the anatomic pattern, the most common pneumonia type was fibrinopurulent bronchopneumonia, non-purulent bronchointerstitial pneumonia and necrotic-fibrinopurulent bronchopneumonia. Necrotic areas were observed in a total of 18 cases. The agent was demonstrated by immunohistochemistry in 24 animals, bronchi and bronchiole epithelium being the most commonly invaded histological structures. Immmo-histochemistry revealed T cell as the most prominent inflammatory cell in M. bovis pneumonia, thus supporting the role of cellular defense in the pathogenesis of this pneumonia in cattle. (C) 2016 PVJ. All rights reserved.