This paper presents the results of the study of the removal of toluene, ethylbenzene, and oxylene (TEX) by biofiltration using a commercial peat as filter-bed material. Runs with a single organic compound in air, and with the mixture of TEX in air, were carried out for at least 55 days in laboratory-scale reactors inoculated with a conditioned culture. The influence of organic compound inlet load and of gas flow rate on the biofilter's performance was studied, including relatively high values of pollutant inlet concentration (up to 4.3 gC m(-3) for ethylbenzene, 3.2 gC m(-3) for toluene, and 2.7 gC m(-3) for o-xylene). Results obtained show maximum elimination capacities of 65 gC m(-3) h(-1) for o-xylene, 90 gC m(-3) h(-1) for toluene, and 100 gC m-3 h-1 for ethylbenzene, and high removal efficiency (> 90%) even for moderately elevated concentrations: 3.0, 2.5 and 1.8 gC m(-3) for ethylbenzene, toluene and o-xylene, respectively. The behaviour of the TEX mixture was in good agreement with the results obtained for the runs in which only one organic compound was present. Ethylbenzene and toluene are degraded easier than o-xylene, and inhibitory effects due to the presence of multiple substrates were not observed. (c) 2005 Society of Chemical Industry