A new technique is developed to study interdiffusion between two miscible metals. The technique is applied to the Ni-Pd system. It consists in measuring the change of apparent surface composition of a Pd substrate coated with an 800 nm Ni thin film during annealing at a given temperature. The measurement is carried out in-situ inside the chamber of a SEM (scanning electron microscope) by EPMA-EDS (electron probe microanalysis-energy dispersive X-ray spectroscopy). The experimental data are processed using a model that mixes the Fick's diffusion equations and the electron probe microanalysis equation. This process allows the determination of the mean interdiffusion coefficient at a given annealing temperature. The main advantages of the technique are the possible determination of interdiffusion coefficients in thin films and at very low temperature (down to 430 degrees C, i.e. similar to 0.4 T-m), which is not achievable with other techniques conventionally used for the study of interdiffusion. The Ni-Pd mean interdiffusion coefficient is shown to follow an Arrhenius law ((D) over tilde (c) = 6.32 x 10(-3) exp(17838 kJ mol(-1)/RT)cm(2) s(-1)) between 430 degrees C and 900 degrees C, in relatively good agreement with previous interdiffusion measurements made on the Ni-Pd system at higher temperature. (C) 2009 Elsevier B. V. All rights reserved.