Polyacrylic acid (PAA) membranes containing alpha-, beta-, or gamma-cyclodextrin (CD) were prepared and used for the separation of o-/p-xylene mixture by pervaporation. It was observed that the native PAA membrane was almost impermeable for the xylene isomers, and the incorporation of CDs in the PAA membranes resulted in membranes having molecular recognition function, which selectively facilitated the transport of the xylene isomers. For all types of CDs, it was found that the facilitated transport occurred at CD concentrations higher than the threshold concentration. As the CD concentration increased, the permeate fluxes increased, while the selectivities were almost constant. The selectivity of the membranes was strongly influenced by the types of CDs incorporated in the membranes. (C) 2003 Elsevier B.V. All rights reserved.