Abstract. The characterization of the BPDA/PDA polyimide (PI) at high temperature up to 400• C, thanks to dielectric relaxation spectroscopy (DRS) in the 10 −1 Hz to 10 6 Hz frequency range, allows the determination of the dc electrical conductivity (σ dc ). In such a high temperature range, the dielectric spectra are modified by the extrinsic electrode polarization phenomenon (EP) response. A model is proposed which coupled to the DRS results allows evidencing and quantifying the effect of the EP. The proposed method gives a simple way to determine the intrinsic σ dc values from the effective ac dielectric response, improving the accuracy and reducing the duration of measurement.