The permeation of p-and m-xylenes through supported liquid membranes (SLM) containing cyclodextrins (CDs) was investigated in this study. Three CDs were used in the experiments, a-CD, b-CD, and hydroxypropyl-b-CD (HP-b-CD). The mass transfer mechanisms with and without facilitating carriers (CDs) were studied individually by applying the solution -diffusion model. The facilitated mass transfer mechanism was elucidated as partitioning of xylenes from the organic phase into an aqueous phase, formation of an inclusion complex with CDs, diffusion of the complex, and extraction into the receiving phase. The formation constants in aqueous solutions for CDs and p-xylene were 1.6-2.4 times higher than that of CDs and m-xylene. The diffusivity coefficient of the xylene -CD complex (D m ) and the 463