A new series of composite, negative temperature coefficient (NTC) ceramics based on the (aY2O3 + bCeO2)-0.4LaCr 0.5Mn0.5O3 (a + b = 0.6) were carefully prepared and related electrical properties were investigated. All the NTC thermistors showed a linear relationship between the natural logarithm of the resistance and the reciprocal of the absolute temperature, indicative of NTC characteristics. The obtained B 25/85 constants were in range of 2,100-2,700 K. The magnitude order of the resistivity at 25 °C was of 10³-10⁹ Ωcm and activation energies varied from 0.185 to 0.231 eV. The aging coefficient of the NTC thermistors with CeO 2 was less than 2 % for the time period of 900 h, suggesting that NTC thermistors with CeO2 possessed a better electrical stability in comparison with CeO2-free thermistors.