Research was conducted for the present paper on microbiological contamination of the air within the City of Toruń. It follows from the studies conducted that microorganisms occurred in greater numbers in the air within the area of the Old Town than in the Rubinkowo residential district. The number of microorgan-isms in the air was subject to seasonal changes. The highest numbers of heterotrophic mesophylic bacteria (CFU 37°C) were found in the summer season and the lowest in the winter season. The majority of isolated bacteria belonged to Gram positive forms - bacilli or cocci. A significant proportion of the isolated bacteria displayed antibiotic resistance to commonly used antibiotics.