A new variant of the nonlineary theory of hysteresis media subjected to nonisothermal loading processes is proposed. It permits description of the functional dependence between stress, deformation and temperature in uniaxial loading conditions. Parameters of the determining equation are established in accordance with the creep diagrams obtained at different fixed temperatures and in accordance with the equation of instantaneous thermomechanical surface. Calculation results for different processes of deformation according to the set processes of loading and heating show a good agreement with experimental data.