The concentrations, distributions, and biomagnification of polybrominated diphenyl ethers (PBDEs) in environmental and biological media in a terrestrial grass ecosystem were studied, The total PBDE concentrations in grasses were 4.00 × 10⁻² to 4.28 ng·g⁻¹. The total PBDE concentration in weasel muscle (23.2 ng·g⁻¹ l.w.) was the highest concentrations of all animal tissue samples, and the total PBDE concentration in hair from local herdsmen (22.2 ng·g⁻¹ l.w.) was second highest. Less-brominated PBDEs were found to be more strongly biomagnified than more-brominated PBDEs in the grassland food web. PBDEs were found to be much more strongly biomagnified in the food chains of homothermic animals than heterothermic animals. More-brominated PBDEs were not markedly biomagnified in the grassland food web. For example, BDE-153 was not biomagnified in the grassland wildlife food chain but was clearly biomagnified through the sheep, cattle, or horse hair to human hair route. The biomagnification factors and log K_ows negatively correlated for the toad–snake, lizard–snake, and mouse–weasel food chains. The ability of PBDE congeners to become enriched generally decreased as the log K_ow increased, and this decrease occurred 100–1000 times more strongly for homothermic animals than heterothermic animals.