The partial conductivities of electrons and holes in yttria stabilized zirconia doped with 5 mol% of TiO2 (5TD-YSZ) have been measured by the d.c.-polarization method using Hebb-Wagner’s asymmetric cell. The partial conductivities of holes, sigma(p), and electrons, sigma(n), were found to be proportional to p(O2)(1/4) and p(O2)(-1/4), respectively, except for sigma(n) in the low p(O2) regime. The sigma(n) values in 5TD-YSZ were greater than those in non-doped ones reported by several investigators. In contrast, the sigma(p) values in 5TD-YSZ were almost the same with those in the non-doped ones. The activation energy for sigma(n) at the fixed p(O2) of 1.0 atm in 5TD-YSZ was smaller than that of the non-doped one, while that for sigma(p) in 5TD-YSZ was almost the same.