Facilitated pertraction of p-aminobenzoic acid (PABA) and p-hydroxybenzoic acid (PHBA) with Amberlite LA-2 and di-(2-ethylhexyl)phosphoric acid (D2EHPA) in pseudosteady-state mode have been comparatively analyzed. The experiments have been carried out using an U-shaped pertraction cell which allowed to easily maintaining the liquid membrane between the two aqueous phases. On the basis of the theoretical investigation, a model describing the solute accumulation inside the liquid membrane by means of the permeability factor has been developed. The proposed model offers a good concordance with the experimental data and can be useful for facilitated pertraction optimization. (C) 2008 Elsevier B.V. All rights reserved.