Using the results of reaction kinetics controlled by anisotropic diffusion, this paper shows that the difference between the diffusional anisotropies of the vacancies and interstitials produces different sink strengths for the two kinds of point defects. The effects on irradiation deformation are investigated in terms of a generalized bias concept that depends not only on the point-defect/sink interaction, as in conventional theories, but also on the diffusional anisotropy difference. It is found that anisotropic diffusion adds a new dimension to the theory of irradiation deformation, which needs to be taken into account in the study of the underlying mechanisms.