The electrical conductivities of the yttria (8mol%) stabilizedzirconia-ceria solid solutions were measured as a function of oxygen partial between 80$0^{circ}C$ and 100$0^{circ}C$ using 4-probe d.c. method Under pure oxygen atmosphere the oxygen ionic conductivity of CeO2-ZrO2 decreased with the concentration of CeO2 Under reducing condition electronic conduction due to the redox equilibrium of Ce ion was observed. Total ionic and electronic conductivities fitted by a defect model enabled to determine the electronic transference number(tei) which increased with the concentration of CeO2 and with the degree of reduction.