In acetone-butanol-ethanol (ABE) fermentation, which is a potential process of producing feed stock chemicals and liquid fuels from renewable biomass, product inhibition is a severe problem affecting the bioconversion. This study is concerned with the separation of acetone-butanol-ethanol (ABE) from dilute aqueous solutions by pervaporation. Poly(ether block amide) (PEBA 2533) membranes were used. The separation of binary acetone-water, n-butanol-water and ethanol-water mixtures by the membranes was initially carried out using a relatively thick (100 mu m) membrane to evaluate the membrane permselecivity, which was found to be in the order of n-butanol > acetone > ethanol. The effects of feed composition, operating temperature and membrane thickness on the membrane performance were studied. It was shown that the boundary layer effect became significant when a thinner membrane (30 mu m) was used, especially for n-butanol separation. In addition, the separation of quaternary acetone-n-butanol-ethanol-water mixtures was also studied, and the potential of the membrane for ABE extraction from dilute aqueous solutions was demonstrated. From an application point of view, the recovery of butanol from the fermentation broth could be a niche application for the membrane. (C) 2004 Elsevier B.V. All rights reserved.