In the present study, the oxygen diffusion in the yttria-stabilized zirconia was investigated under various stress conditions by means of the molecular dynamics simulation. With the uniaxial tensile stress, the oxygen ions preferentially migrate in the tensile direction and hardly in the other vertical direction without changing the total diffusion property. On the other hand, the uniaxial compressive stress deteriorates the oxygen diffusion in the compressive direction, which has the highest activation energy. These effects are clearly observed with the stress above 1 GPa and could be attributed to the elastic strain energy. For the case of the hydrostatic stress, the dilation by the tension increases the total oxygen diffusion whereas the shrinkage by the compression deteriorates it, which can be considered as the accumulative effect of the uniaxial stress in each direction. The present result indicates that the ionic conductivity of the yttria-stabilized zirconia could be enhanced by applying directional stresses. (C) 2010 Elsevier B.V. All rights reserved.