This paper describes the application of a manometric method for the determination of the chemical diffusion coefficient for the electrode material (La0.8Sr0.2)MnO3 in the temperature range 500-850 degreesC. In the manometric method, the progress of a chemical reaction, such as oxygen incorporation into a non-stoichiometric oxide, can be monitored by the determination of changes in oxygen partial pressure. It was observed that the diffusion data obtained for oxidation and reduction differ essentially in both absolute values and their temperature dependence. (C) 2000 Elsevier Science BN. All rights reserved.