The present study was intended to investigate pathologically and microbiologically all organs of the respiratory systems of chickens taken from flocks in laying hens enterprises in and around Konya that had respiratory system problems and to reveal the distribution of lesions in the relevant system, their characteristics and their connection with the microbiological results. For the study, 192 chickens were taken from 33 coops and necropsies were conducted on them. In histopathological examination, lesions in epithelium and propria were separately scored as mild (+), medium (++) and severe (+++).It was found that macroscopic findings were common findings that could be encountered in all infections of the respiratory system, and the whitish foci as big as a pinhead in the mucuous membranes indicated severe lymphoid cell infiltration in propria and lymphoid hyperplasia. It was thought that the caseous masses encountered in the lumens of the examined organs could be related with infections of Mycoplasma gallisepticum and E.coli.

It was the lung from which the infectious agents (n: 43) isolated mostly and S. aureus (n: 50) was the causative that isolated most frquently, taken together it was considered that to diagnose such infections in the laboratory immunoperoxidase and molecular techniques along with pathological and microbiological examinations should be made use of.