Respiratory exposure to organic dust induces chronic pulmonary diseases both in farmers and horses. The aim of this study was to examine the variation of dustiness and hygiene quality of peat moss bedding. Materials studied were weakly decomposed sphagnum peat (A), weakly decomposed sphagnum peat warmed up in storage (>30 degrees C) (B) and two more decomposed few-flowered sedge peats (C and D). The geometric mean of mesophilic fungi, thermotolerant fungi and thermophilic actinomycetes were determined from the material. Samples of inhalable dust and endotoxins were collected with IOM samplers and respirable dust with 10M foam samplers when the peat was rotated in a cylinder. The number of particles was detected with an optical particle counter. An LAL assay was used for analysing endotoxins from thefilter samples. There were differences in the hygiene quality and dustiness between peat materials (p<0.01). The geometric mean of fungi was smallest in material A. Warming-up increased the number of fungi in sphagnum peat, but on the other hand, it decreased the content of endotoxin (p <0.01). Few-flowered peat materials contained thermophilic actinomycetes and material D also contained Aspergillus fumigatus. The concentrations of inhalable dust, respirable dust and the number of particles were smaller in thefew-flowered peats (C-D) than in the sphagnum peats (A-B). It is concluded that there are differences in the dustiness and hygiene quality of peat bedding.