Ion-exchange membranes modified with sulfonic (-SO₃H) and phosphonic acid (-PO₃H) groups were prepared by radiation-induced grafting of glycidyl methacrylate (GMA) onto polyethylene (PE) films and sub-sequent sulfonation and phosphonation of poly(GMA) graft chains. The surface area, thickness and volume of grafted PE film increased with increasing grafting yield. The specific electrical resistance of PE membrane modified with the -PO₃H and -SO₃H groups decreased with increasing the ion-exchange capacity. The PE membrane modified with -PO₃H group had a lower specific electrical resistance than that of PE membrane modified with -SO₃H group.