Microbiological air sampling was performed in four sawmills located in eastern Poland, of which two were processing coniferous wood (pine, fir) and other two deciduous wood (oak, birch). Total concentration of microorganisms (bacteria and fungi) in the air of sawmills processing coniferous wood was on average 20.2 +/- 5.6 x 10³ cfu/m³ (mean +/- S.E.) and significantly (p<0.05) higher compared to those processing deciduous wood where the mean concentration of airborne microorganisms was 9.8 +/- 3.0 x 10³ cfu/m³. The greatest concentrations of microorganisms in the sawmills processing coniferous wood were noted at debarking and at first-cut frame sawing of pine logs (42.1 +/- 7.6 x 10³ cfu/m³ and 39.8 +/- 7.0 x 10³ cfu/m³, respectively). Microflora released into air during debarking consisted mostly of allergenic fungi (mainly Aspergillus fumigatus) and corynebacteria, whereas airborne microflora recovered during first-cut frame sawing constituted mostly of endotoxin-producing Gram- negative bacteria of the genus Rahnella, developing in the sapwood of pine. In the sawmills processing deciduous wood, the largest concentration of microorganisms (30.6 +/- 3.4 x 10³ cfu/m³) was found at sorting of the oak parquet boards and was due to the secondary infection of the boards with moulds Penicillium citrinum during prolonged storing in the open air. Values of the respirable fraction of airborne microflora in the examined sawmills varied within fairly wide limits and were between 22.5 86.6%. Altogether, 34 species or genera of bacteria and 21 species or genera of fungi were identified in the air of sawmills, of which respectively 13 and 9 species or genera were reported as having allergenic and/or immunotoxic properties. The concentrations of airborne bacterial endotoxin which were determined on two sampling sites in the sawmills processing pine and fir, were 0.24 microg/m³ and 4.00 microg/m³ respectively, distinctly exceeding the suggested safe level. In conclusion, the workers of Polish sawmills may be exposed on some working stands to airborne microorganisms posing respiratory hazard, of which the greatest risk is represented by allergenic fungi developing on bark of logs or stored wood products and endotoxin-producing Gram-negative bacteria of the genus Rahnella, developing in sapwood of coniferous logs.