A phenomenological theory of the Kirkendall effect is presented, taking into account the point defect production by plastic deformation. General relations are derived for the vacancy distributions and for the displacement velocities of inert markers, accounting also for the concentration dependence of the lattice constants. By simple approximation assumptions the vacancy distribution within the diffusion zone is explicitely calculated. The application of the theory to measurements by Heumann and Walther on gold-silver diffusion couples indicates that defect production due to plastic deformation is considerable, of the order of 10 −5 defects per second and lattice site. The number of generated vacancies is unambiguously larger than that of interstitials. The influence of interstitials on the diffusion is, however, negligibly small, since their lifetime is found to be small as compared to the lifetime of the vacancies. It is also found that in the considered experiment the deviation from vacancy equilibrium inside the diffusion zone is not more than 0.3%. The phenomena near the boundaries of the diffusion zone indicate, however, a definite vacancy supersaturation, which is caused by the plastic deformation.