We argue that use of certain electrode assemblies adversely affects the measured spectra of both epsilon' and tan delta (=epsilon ''/epsilon') and thus violates an aspect of the Kramers-Kronig relations. The values of epsilon(s), epsilon(c), and tan delta measured are not the true values of the sample and their analysis leads to questionable conclusions. Some of the data in the literature can be corrected for this effect if the epsilon'-spectra are available. Such electrode assemblies also yield erroneous values of tan delta measured for studies of structural relaxation. Also, the electrical modulus, M* =1/epsilon*., spectra of ion-containing materials violate the Kramers-Kronig relations because M' and M '' values contain contributions from electrode polarization, in addition to the electrode spacer effects. Fitting of the relaxation functions to such data or analyses of the spectral-differences may be misleading. (C) 2012 Elsevier B.V. All rights reserved.