The influence of thermal expansion on thermally stimulated currents has been studied by means of model calculations based on the bistable model of Fro¨hlich, considering especially the case of materials characterized by expansion coefficients markedly different above and below the relaxation range. A good qualitative and quantitative agreement has been obtained between theory and experiment in elastomeric materials (styrene‐isoprene‐styrene and isoprene‐styrene‐isoprene block copolymers) showing that thermal expansion is the main factor responsible for the appearance of current reversals in thermally stimulated polarization processes.