The presented research aimed at determining the species composition and concentration of colony forming units (CFU) in two types of cattle barns for dairy cows and in a calf barn. The study was carried out in winter and summer 2012. The measurements took place in a free stall and tie stall barn and, additionally, in a calf barn. The mycological analysis of the air was conducted using the impact method, with an Air Ideal 3P apparatus. Spores of 45 species of fungi were found in cattle barn air, among them 36 species were collected in winter and 30 in summer. The fungal population was characterized by considerable variation across the seasons of the year and between bar types. The species most abundant irresepective of the season was Cladosporium herbarum. Winter conditions favored Penicillium nigricans, whereas summer was conducive to the development of Rhodotorula glutinis. The concentrations of fungal spores determined in the study were not a direct hazard to barn workers or animals.