Two to ten nanometer thick polycrystalline Pd films were prepared on the (111) surface of Ag single crystal and investigations of the Ag diffusion along Pd grain boundaries were carried out using the Hwang-Ballufi method. The samples were monitored by Auger electron spectroscopy (AES) during isothermal heat treatments in the 438-563 K temperature range. Using plausible simplifying assumptions, the activation energy of the product of the grain boundary (GB) diffusion coefficient and k' (k' = c(s)/c(gb); c(s) and c(gb) are the surface and GB concentration, respectively) was calculated (0.99 +/- 0.08 eV) from the evaluated saturation coefficients of the surface accumulation. This energy, for weak temperature dependence of k', is approximately equal to the activation energy of the GB diffusion. (C) 2008 Elsevier B. V. All rights reserved.