Ion transport studies on polyethylene oxide (PEO) based nanocomposite polymer electrolyte (NCPE) membranes (PEO: NH4HSO4) dispersed with nanosized SiO2 particle in varying wt.(%) have been reported. NCPE films have been cast by a novel hot-press (extrusion) technique. Scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infra-red (FTIR) spectroscopy, ionic transport number (t(ion)) and electrical conductivity (sigma) studies have been carried out on hot-press films and the results have been compared with NCPE films prepared by the standard solution cast technique. As a consequence of dispersion of a fractional amount of nanosized SiO2 filler particles into the polymer-salt complex (PEO: NH4HSO4) host matrix, an enhancement of approximately an order of magnitude in the room temperature conductivity resulted. NCPE membranes with SiO2 content: 5 wt.% (Solution cast) and 15 wt.% (hot-press) exhibited optimum room temperature conductivity (sigma) values similar to 2.5 x 10(-4) S cm(-1) and similar to 1.4 x 10(-4) S cm(-1), respectively. Two maxima appeared in the SiO2 concentration dependent conductivity plot for hot-pressed NCPE films which are discussed in the light of an existing two percolation threshold model. (C) 2008 Elsevier B.V. All rights reserved.