The literature of SOFC electrode kinetics and mechanisms is full of contradicting details in case of both the SOFC anode and cathode processes. Only weak patterns may be identified. One interpretation is that each of the reported data sets reflects a laboratory specific nature of each of the electrodes because the data sets are difficult to explain by differences in overall composition and structure. Therefore, we suggest the idea of serious effects of foreign phases due to impurities and/or segregation of cell constituents. Such foreign phases will depend very much on raw material purity and synthesis procedures. The paper deals with the available evidence and gives some possible explanations of observed phenomena, e.g. of the various reported effects of water and of the temperature dependence of H/D isotope effect on the SOFC anode. (C) 2002 Elsevier Science B.V. All rights reserved.