The O-18/O-16 isotope exchange depth profile technique (IEDP) followed by SIMS characterizations was applied to dense membranes of pure ionic conductors and mixed ionic/electronic conducting materials. It is a very useful tool since we obtain in both cases data concerning the oxygen diffusion in the bulk and the oxygen exchange at the surface of the materials. Comparisons were done, including results concerning the role of the surface with regards to the oxygen reduction reaction. Detailed experimental and analytical processes are given. (c) 2005 Elsevier B.V. All rights reserved.