Background: The aim of the study was to quantitatively and qualitatively identify moulds occurring in the air of selected office rooms. Material and Methods: The study was conducted in the wintertime inside four office rooms with moisture trace and one control room. To assess mycological contamination of the air, triple samples were directly collected on Petri dishes (Malt Extract Agar medium) using a Burkard air sampler. Qualitative evaluation of moulds was based on the microscopic view and morphological features of colonies. Results: Total number of moulds determined in the air of office rooms did not exceed the level of 4x102 cfu/m3. The highest concentration of moulds (3.44x102 cfu/m3) was found in the room that was also used as an archive. It was over tenfold higher than in the control room (0.33x102 cfu/m3). The qualitative analysis of moulds showed the presence of 15 species. Some of them, including Aspergillus fumigatus, Aspergillus versicolor, Aspergillus ochraceus, Cladosporium spp., Penicillium spp. and Alternaria spp., are recognized as potential health hazards to workers due to the production of mycotoxins and allergic reactions. Conclusions: The archive was the only room, where concentration of moulds slightly exceeded the reference value. To protect the health of workers who perform their duties in this place, the documents, which are an ideal place of mould growth, should be moved to a separate room. Respiratory complaints reported by workers could be associated with concentrations and species of moulds found in the office rooms under study. Med Pr 2007;58(6):521-525