In this study, a membrane biofilm reactor performance for toluene as a model pollutant is presented. A composite membrane consisting of a porous polyacrylonitrile (PAN) support layer coated with a very thin (0.3 mu m) dense polydimethylsiloxane (PDIVIS) top layer was used. Batch experiments were performed to select an appropriate inocula (slaughterhouse wastewater treatment sludge with a specific toluene consumption rate of 118 +/- 23 mu g g(-1) VSS L(-1)) among the three available sources of inoculums. The maximum elimination capacity gas-side reactor volume based (EC)(v) and membrane based (EC)(m, max) obtained were 609 g m(-3) h(-1) and 1.2 g m(-2) h(-1) respectively, which is much higher than other membrane bioreactors. Further experiments involved the study of the membrane biofilm reactor flexibility when operational parameters as temperature, loading rate etc. were modified. In all cases, the membrane biofilm reactor showed a rapid adaptation and new steady-states were obtained within hours. Overall, the results illustrate that membrane bioreactors can potentially be a good option for treatment of air pollutants such as toluene. (c) 2008 Elsevier Ltd. All rights reserved.