Two identical sized laboratory-scale biofilters, filled with the same type of packing material, consisting of a mixture of peat and glass beads in a 4:1 volume ratio, are investigated for the purification of toluene and styrene-containing off-gas streams. One of the biofilters was inoculated with a toluene-degrading strain of Acinetobacter sp. NCIMB 9689, and the other with a styrene-degrading strain of Rhodococcus rhodochrous AL NCIMB 13259. For both pollutants, different sets of continuous experiments were conducted in the biofilter columns, varying both the inlet pollutant concentration and the superficial gas velocity. Maximum elimination capacities of 242 and 63 g m(packing material)(-3) h(-1) packing material were recorded for toluene and styrene, respectively. Furthermore, the deodorization (defined as the achievement of a pollutant concentration in the effluent gas below the pollutant olfactory threshold value) of toluene and styrene-containing waste-gases was also considered. This was achieved, operating at maximum inlet concentrations of 1.99 and 0.20 g m(-3) and at superficial gas velocities of 17.8 and 122 m h(-1), respectively.