Microbiological air sampling was performed in a big potato processing plant located in eastern Poland. Air samples for determination of concentrations of microorganisms, dust and endotoxin were collected at 6 sites in the division producing potato flakes and meal from dried potato pulp and at 2 sites in the division producing potato syrup from imported starch. The concentrations of total airborne microorganisms were within a range of 28.3-93.1 x 10³ cfu/m³. Mesophilic bacteria were dominant at all sampling sites, forming 73.1-98.8% of the total count. Among them, distinctly prevailed corynebacteria (irregular Gram-positive rods) that accounted for 54.3-81.1% of the total airborne microflora. The most common were strains of Corynebacterium spp., followed by strains of Arthrobacter spp., Microbacterium spp., and Agromyces ramosus. The latter species, so far not reported from the air of occupational environments, abundantly develops in the parenchyma of potato tubers. Its airborne concentration increased rapidly after peeling of potatoes, and attained maximal values at cutting and blanching (steaming and sulfuration) of potatoes, and at sacking of potato meal. The proportions of Gram-negative bacteria and endospore-forming bacilli were low, respectively 0.6-7.6% and 2.0-8.1% of total count. Fungi constituted 1.2-26.9% of total count. The dominant species was Aspergillus niger that formed 99.8% of total airborne fungi. The values of the respirable fraction of airborne microflora varied between 25.3-73.2%. The concentrations of airborne dust were 1.4-26.6 mg/m³ in the division producing potato flakes and meal and 114.9-200.5 mg/m³ at pouring of potato and corn starch for syrup. The concentrations of airborne endotoxin were in the range of 0.011-0.089 microg/m³ during the initial stages of potato processing (unloading, washing, peeling) and drastically increased after blanching to the extraordinarily high levels of 45.9-1893.9 microg/m³. At pouring of starch for syrup, the concentrations of airborne endotoxin were much lower, within a range of 0.029-0.156 microg/m³. In conclusion, the workers of potato processing facilities could be exposed to large concentrations of microorganisms, dust and endotoxin posing a risk of work-related respiratory disease.