Polymeric electrolytes consisting of oligo(ethylene oxide)-grafted polymethacrylate (PEO-PMA) matrix, linear polyether and magnesium salts have been prepared, and their electrochemical behavior as solid Mg2+ ion conductors has been examined. Thermal analyses showed that the obtained polymeric electrolytes are homogeneous and amorphous over a wide temperature range. The conductivity depended much on the kind of the dissolved magnesium salt. The highest conductivity was obtained for the polymeric electrolyte containing Mg[(CF3SO2)(2)N](2) (>10(-4) S cm(-1) at room temperature). The dc polarization of a Pt/Mg cell using the polymeric electrolyte proved that Mg2+ is mobile in the present polymeric system. A prototype cell was constructed using the polymeric electrolyte with a Mg (or Li) anode and a V2O5 Cathode, where the intercalation-deintercalation of Mg2+ occurred reversibly.