The aim of this study was to determine the levels of microorganisms, dustand endotoxin in the air during various stages of valerian (Valeriana officinalis) roots processing byherb farmers and to examine the species composition of airborne microflora. Air samples were collectedon glass fibre filters by use of personal samplers on 15 farms owned by valerian cultivating farmers,located in Lublin province (eastern Poland). The concentrations of total viable microorganisms (bacteria+ fungi) in the air showed a marked variability and were within a range of 0.95-7,966.6 x 10(3) cfu/m(3). Though median was relatively low (10.75 x 10(3) cfu/m (3)), on 4 farms the concentrations exceededthe level of 10(5) cfu/m (3) and on 1 farm the level of 10(6) cfu/m (3). During the processing of valerianroots, distinct changes could be observed in the composition of airborne microflora. In the first stagesof processing, the freshly dug and washed roots until shaking in the drying room, the most numerous wereGram-negative bacteria of the family Pseudomonadaceae (mostly Stenotrophomonas maltophilia, Pseudomonaschlororaphis and Pseudomonas fluorescens). After drying, the dominant organisms were thermo-resistantendospore-forming bacilli (Bacillus spp.) and fungi, among which prevailed Aspergillus fumigatus. Altogether,29 species or genera of bacteria and 19 species or genera of fungi were identified in the farm air duringvalerian processing, of these, 10 and 12 species or genera respectively were reported as having allergenicand/or immunotoxic properties. The concentrations of airborne dust and endotoxin on the examined farmswere very large and ranged from 10.0-776.7 mg/m (3), and from 0.15-24,448.2 microg/m (3), respectively(medians 198.3 mg/m (3) and 40.48 microg/m (3)). In conclusion, farmers cultivating valerian could beexposed during processing of valerian roots to large concentrations of airborne microorganisms, dustand endotoxin posing a risk of work-related respiratory disease.