Diffusion in a Pd/Ag monocrystalline system with various dislocation densities has been studied in the temperature range from 670 to 770 K. In silver the diffusion coefficient is independent of the dislocation density, in palladium the diffusion coefficient increases with the growth of the dislocation density. It is inferred that diffusion in silver occurs by volume diffusion, as for palladium, the diffusion proceeds along moving the dislocations.