Current‐voltage characteristics of polycrystalline silicon films highly doped with phosphorus and boron were studied over a wide range of temperatures (40–300 K) and applied electric fields (up to 5 kV cm−1). After the usual ohmic regime, we observed a large increase in dc current versus applied voltage. Moreover, at higher electric fields, a new ohmic conduction regime appeared which has not yet been reported in polycrystalline silicon. Thermoemission‐based models cannot fully interpret our results. We present a new interpretation of current‐voltage characteristics based on a model previously used to interpret the electrical properties of these films at low electric fields. This model takes into account the existence of fluctuations both in intergranular potential and in the grain boundary barrier heights. They result from all of the macroscopic inhomogeneities due to the growth conditions of the material. The high electric field detraps carriers from grain boundaries and extracts the carriers located in the valleys of potential created by the fluctuations, thus inducing transition in conductivity.