The electrochemical performance of solid oxide fuel cells with cathodes made of , , , , and has been investigated. As reference, electrochemical data from cells with cathodes were taken into account. The cathode layers were sintered at various temperatures. After testing, cross-sectional analyses were made in order to investigate microstructural changes in the various layers. Electrochemical tests have shown that only cells with a non-sintered Cu-containing cathode or with a similar cathode treated with relatively low sintering temperatures can be considered for SOFC applications. However, it was clear that the tested cells with cathodes including Cu and/or Ni showed electrochemical performance which was always lower than that of reference cells with cathode. No electrochemical measurements were possible with cathodes sintered at or above . Cross-sectional analyses revealed that in all these cases the presence of Cu exhibited severe chemical interaction with the electrolyte. In addition, several undesired phases were formed in the cathode as well as in the diffusion barrier layer. The extent of these phases and the interaction with the electrolyte layer increased with increasing sintering temperature.