Air sampling was performed during picking and sorting of hop (Humulus lupulus)cones on 19 hop farms located in eastern Poland. The concentration and composition of airborne microfloraand the concentration of airborne dust and endotoxin were determined. Additionally, 7 samples of settledhop dust were collected and examined for the presence of microorganisms and endotoxin. Total concentrationsof airborne microorganisms were within a range of 2.08-129.58 x 10(3) cfu/m(3). Gram-positive bacteriaformed 22.2-96 % of the total count. Among them, prevailed corynebacteria and endospore-forming bacilli.Fungi constituted 3.7-65.4 % of the total count. The dominant species were Penicillium citrinum, Alternariaalternata, and Cladosporium epiphyllum. Thermophilic actinomycetes and Gram-negative bacteria were detectedin the air of only 10 and 6 farms, respectively. Airborne dust concentrations at the workplace rangedfrom 0.17-31.67 mg/m(3). The concentrations of airborne endotoxin were in the range of 26-6250 ng/m(3).In the samples of settled dust, the concentrations of total microorganisms ranged from 0.25 x 10(6) to2.87 x 10(8) cfu/g. Gram-positive and Gram-negative bacteria constituted respectively 3.2-98 % and 0-93.5% of the total count. Fungi formed 0-30.3 % of the total count. The most common species were Penicilliumspp. and Alternaria alternata. The concentrations of endotoxin were in the range of 312.5-6250 microg/g(median 6250 microg/g). The presence of microorganisms and endotoxin in the samples of settled dust wasconfirmed by electron microscopy. The hop growers seem to be exposed to lower concentrations of dust,microorganisms and endotoxin compared to other branches of agriculture. This may be partly due to antimicrobialproperties of hop plant. Among microbial factors associated with hop dust, bacterial endotoxin and allergenicfungi pose the greatest potential hazard for exposed hop farmers.