Polymer electrolyte membranes that consist of poly(vinyl acetate) (PVAc) and LiClO4 with different concentrations of plasticizer (N,N-dimethylformamide (DME) have been prepared by a solution-casting technique. The formation of polymer-salt complexes has been confirmed by FT-IR spectral studies. Conductivity studies have been carried out using ac impedance spectroscopy in the frequency range 42 Hz-5 MHz. The influence of the addition of plasticizer (DMF) on the ionic conductivity of the PVAc-LiClO4 polymer electrolyte complex has been discussed. The maximum value of bulk conductivity for PVAc(70)-DMF(20)-LiClO4(10) system is found to be 4.2 x 10(-4) S cm(-1) at 303 K. The temperature dependence of the conductivity of the polymer electrolytes follows the Vogel-Tamman-Fulcher relationship. Transport properties, such as activation energy and charge carrier concentration, have been calculated from the VTF formalism. The ionic transference number of the mobile ions has been estimated by Wagner's polarization method and is found to be greater than or equal to0.96 for all the samples. (C) 2004 Elsevier B.V. All rights reserved.