Thin films of poly(vinylchloride) (PVC)/poly(methylmethacrylate) (PMMA) blend polymer electrolytes plasticized with a combination of ethylene carbonate (EC) and propylene carbonate (PC) and LiN(CF3SO2)(2) as salt have been prepared by solution casting technique. The prepared films were subjected to a.c. impedance measurements as a function of temperature ranging from - 30 to 70 degreesC. Also, PVC/PMMA composite electrolytes were prepared using TiO2 as inorganic filler. The effect of liquid plasticizer and inorganic filler on the interfacial stability of the blend polymer electrolytes was studied. The prepared films were also subjected to TG-DTA analysis and the results were discussed.