Microbiological air sampling was performed on 5 flax farms located in easternPoland. Air samples for determination of the concentrations of microorganisms, dust and endotoxin werecollected in barns during machine scutching of flax stems by the farmers. The concentrations of mesophilicbacteria ranged from 203.5-698.8 x 10(3) cfu/m3, of Gram-negative bacteria from 27.2-123.4 x 10(3) cfu/m3,of thermophilic actinomycetes from 0.5-2.6 x 10(3) cfu/m3, and of fungi from 23.4-99.8 x 10(3) cfu/m3.The concentrations of total airborne microorganisms (bacteria + fungi) were within a range of 245.0-741.0x 10(3) cfu/m3. The values of the respirable fraction of total airborne microflora on the examined farmswere between 45.5-98.3%. Corynebacteria (irregular Gram-positive rods, mostly Corynebacterium spp.) weredominant at all sampling sites, forming 46.8-67.8% of the total airborne microflora. Among Gram-negativebacteria, the most numerous species was Pantoea agglomerans (synonyms: Erwinia herbicola, Enterobacteragglomerans), known to have strong endotoxic and allergenic properties. Among fungi, the allergenic speciesAlternaria alternata prevailed. Altogether, 25 species or genera of bacteria and 10 species or generaof fungi were identified in the farm air during flax scutching; of these, 11 and 6 species or generarespectively were reported as having allergenic and/or immunotoxic properties. The concentrations ofairborne dust ranged within 43.7-648.1 mg/m3 (median 93.6 mg/m3), exceeding on all farms the Polish OELvalue of 4 mg/m3. The concentrations of airborne endotoxin ranged within 16.9-172.1 microg/m3 (median30.0 microg/m3), exceeding at all sampling sites the suggested OEL value of 0.2 microg/m). In conclusion,flax farmers performing machine scutching of flax could be exposed to large concentrations of airbornemicroorganisms, dust and endotoxin, posing a risk of work-related respiratory disease.