Pathologies of the respiratory system are accompanied by the formation of a multicomponent microbiocenosis. Microorganisms isolated from the respiratory tract have different degrees of priority in the development of pathological processes. In waterfowl, from pathologies of fungal etiology, visceral aspergillosis with localization of the pathological focus in the respiratory tract is more common. Aspergillosis is characterized by a chronic course with various forms that can pass into one another and be supplemented by bacterioses. The aim of the work is to determine the spectrum of microbial agents in the fungal-bacterial association isolated from the lungs of a swan. The object of the study was the corpse of a hissing swan. In the course of the work, such methods as autosection, histological, microscopic, mycological, bacteriological were used. Macroscopically revealed signs characteristic of bronchopneumonia complicated by aerosacculitis. There are two types of limited foci in the lungs and air-carrying bags with a diameter from 3 cm to˂0.2 mm. Four groups of prokaryotes Pseudomonas aeruginosa, Proteus mirabilis, Echerichia coli, Staphilococcus aureus, and the microscopic fungus Aspergillus fumigatus were isolated from the lungs. The leading pathogen in the development of pathological changes in the lungs of a swan is smoking aspergillus. The isolation of representatives of enterobacteria from the lung tissue may indicate contamination of the studied material post mortem, and not the etiological significance of these bacteria. However, any negative effect causing suppression of immune defense mechanisms can stimulate the activity of microorganisms that, isolated or only in combination, can cause a pathological process in the respiratory tract. In this regard, the influence of microflora and the role of isolated microbial associates in the development of respiratory tract pathologies should not be underestimated.