The separation performance of radioactive iodine from radioactive waste is examined using the paper membrane made of long length pulp fiber bearing trimethylhydroxypropylammonium anion exchange group. Prepared paper membrane is sturdy and high of ion-exchange capacity as the introduction of ion exchange group into the paper membrane with high density and well-bonding between pulp fibers are achieved. Ion transport across the paper membrane is evaluated with electroconductive membrane permeability derived from transmembrane potential and membrane conductance data, and diffusional membrane permeability derived from transmembrane potential and ionic flux in (NaI)-I-125 or (NaCl)-Cl-36 single electrolyte concentration-cell system. The ratio of electroconductive membrane permeability of I-125 to that of Cl-36 reaches 6.2, while the ratio of diffusional membrane permeability of I-125 to that of Cl-36 is almost unity. The novel prepared paper membrane exhibits the I-125 permselectivity by solution/membrane distribution process due to electrostatic effect. (C) 2003 Elsevier B.V. All rights reserved.