Mobilities of electrons ($mu_p$) and holes ($mu_p$) in 2, 5, and 10 mol% $TiO_2$-doped yttria stabilized zirconia (TD-YSZ) have been estimated by a non-steady state gas permeation method using models proposed by Weppner and Maruyama. Values of $mu_n$ and $mu_p$ were found to be closed to those in non-doped YSZ reported earlier. The concentration of electrons and holes were calculated from $mu_n$ and $mu_p$ values and the partial conductivities of electrons and holes measured by a dc-polarization method. The concentration of electrons at unit oxygen partial pressure increased with increasing $TiO_2$concentration, while the hole concentration was almost independent of $TiO_2$concentration.