Modification caused in cellophane matrix (a highly hydrophilic natural polymer) by gamma-irradiation was studied by determining changes in different electrochemical parameters obtained from measurements carried out with the membranes in contact with NaCl and MgCl2 solutions. Three different irradiation doses (10 Gy, 30 Gy and 80 Gy) were used in order to consider its possible effect in membrane modification. Changes in salt permeability, electrical resistance and permselectivity show modifications in the membrane matrix, which seem to produce: (i) a reduction in the inter-chains free space (around 40 %), which slightly decreases when the irradiation dose increases (20 % at the highest dose); (ii) an increase of the cation-exchange character of cellulose membranes, which is directly dependent on the irradiation doses (between 10 % and 20 %). Salt permeability and electrical resistance hardly depend on the kind of electrolyte, but higher values were obtained for cationic membrane permselectivity with NaCl solutions for both pristine and irradiated samples. (c) 2005 Elsevier B.V. All rights reserved.