Free standing polymer electrolyte films comprising of ammonium trifluoromethane sulfonate in poly(ethyl methacrylate) were prepared and characterized. The structural and electrical properties of the polymer electrolytes were investigated by X-ray diffraction and a.c. impedance spectroscopy, respectively. The formation of polymer-salt complex has been confirmed by Fourier transform infrared spectroscopy study. Conductivity of the polymer electrolytes increased with salt content. The highest ionic conductivity in the order of 10-5 S cm-1 at room temperature was achieved for the system with 35 wt% of ammonium salt. The temperature dependence of conductivity obeyed the Vogel-Tammam-Fulcher relation. The activation energy has been calculated from the VTF formalism. The ionic transference number of the mobile ions estimated by Wagner’s polarization method was close to unity for the highest conducting sample implying that the conductivity was contributed by ions which was expected to be protons.