New Na+ ion conducting composite polymer electrolytes comprising of polyethylene oxide (PEO)-NaClO4 and PEO-NaI complexes dispersed with SnO2 are reported. The results of the studies based on optical microscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infra-red (FTIR) spectroscopy, impedance analysis and mechanical testing are presented and discussed. The electrical conductivity of approximate to 5.10(-5) S.cm(-1) at 40 degrees C was achieved for the dispersion of approximate to 10 wt.% of SnO2 in both systems. The composition dependence of the conductivity has been well correlated with the variation in glass transition temperature and degree of crystallinity. A substantial enhancement in the mechanical properties of the composite films was observed at the cost of slight decrease in the conductivity at higher concentration of SnO2. The temperature dependence of the conductivity follows apparently the Arrhenius type thermally activated process below and above the melting temperature of PEO. The conductivity of the materials has been found to be strongly humidity dependent. The materials are shown to be ionic with t(ion) > 0.9. The electrochemical stability of the materials has been observed to be up to approximate to 3.2 V for (PEO)(25)NaClO4 + x% SnO2 and is limited to approximate to 1.9 V for (PEO)(25)NaI + x% SnO2.