The chemical diffusion coefficient and the ionic conductivity of the fast mixed conductor alpha’-Ag2+deltaTe have been measured with high stoichiometric resolution at 160 and 200 degrees C within the range of homogeneity by applying both ac and de methods. All measurements were performed on the same symmetric electrochemical cell. The stoichiometry of alpha’-Ag2+deltaTe was varied in situ by coulometric titration with AgI as a solid ionic conductor. Chemical diffusion coefficients and silver ionic conductivities are available from the transient voltage response of the ionic probes during polarization/depolarization experiments as well as from an analysis of the impedance data using an equivalent circuit model. The ac and de results regarding the composition dependence of the chemical diffusion coefficient and the ionic conductivity of alpha’-Ag2+deltaTe are in full agreement with each other within the Limits of error.