Two capillary porous membrane bioreactors (MBRs) were used in series to treat xylene mixture and the performance of MBRs was studied. No inhabitation between the removal of o-, m-, p-xylene was found. A maximum xylene elimination capacity reached 409 g m(-3) h(-1) (ECv,max = 102 mg m(-3) h(-1)) at a gas residence time of 9 s. The estimated yield coefficient (Y), determined from the carbon dioxide production, reached 0.73 g (VSS) g(-1) (xylene) and 0.89 g (VSS) g(-1) (xylene) under operation conditions with nutrient (I) and (II), respectively. The results implied that MBRs could become one of the best available technologies for the reduction of VOC emissions in the chemical sector. (C) 2013 Elsevier B.V. All rights reserved.