This paper deals with the analysis of the effect of temperature gradient applied to polymeric cables on space charge accumulation inside insulation bulk. In particular, experimental measurements on HVDC cable models showed that space charge due to temperature gradient is generally negligible with respect to excess charge injected from the electrodes at electrical fields larger than the threshold for space charge accumulation. The effect of temperature gradient can be revealed only at fields close to the threshold, i.e. 5 to 10 kV/mm, leading, however, to a small extent of charge accumulation, of the order of tens of mC/m3.