A novel bioreactor packed with ceramic monolith colonized by a toluene-degrading culture was investigated in order to assess its suitability for waste gas treatment. Operational parameters that were considered included start-up of the bioreactor, toluene loading rate, changes in gas flow rate, liquid feed mode, and steady-state operation. This is the first report on the treatment of toluene-polluted air in such a biological monolith reactor. Data on performance and stability have been obtained showing that this system is suitable for waste gas treatment. Removal efficiencies around 90% could be maintained at different gas flow rates, although this value gradually dropped when increasing the load above 30 g m(-3) h(-1). Interestingly, omitting the continuous feed of a liquid trickling phase improved the reactor's performance. One potential drawback that needs to be minimized is related to clogging after long term operation. Further studies aimed at optimizing this novel application would allow reaching a high performance under long-term, stable conditions.