The addition of nanometric fillers (e.g., SiO2, TiO2) to P(EO)(n)LIClO4 polymer electrolytes induces consistent improvement in the transport properties. The increase in conductivity and in the cation transference number is attributed to the enhancement of the degree of the amorphous phase in the polymer matrix, as well as to some acid-base Lewis type, ceramic-electrolyte interactions. This model is confirmed by results obtained from a detailed impedance spectroscopy study carried out on poly(ethylene oxide) [P(EO)]-based polymer electrolyte samples with and without ceramic fillers.