The films of polyaniline:polyethyleneterephthalate films were prepared by polymerizing aniline soaked in polyethyleneterephthalate films of different thicknesses. The films were characterized by FTIR as well as for their electrical properties. The electrical properties of the films were observed to be of good quality as almost all the films showed a great increase in their electrical conductivity from insulator to semiconductor region after doping with hydrochloric acid. All the films in their doped state follow the Arrhenius equation for the temperature dependence of electrical conductivity from 35 to 115oC. The thermooxidative stability was studied by thermogravimetry and differential thermal analysis. The stability in terms of dc electrical conductivity retention was also studied under ambient conditions by two slightly different techniques viz. isothermal and cyclic techniques. The dc electrical conductivity of the films was found to be stable below 90oC for all the films under ambient conditions.