Oxygen surface exchange kinetics of La.sub.0.7A.sub.0.3MnO.sub.3±delta has been studied by the isotope exchange method with gas phase equilibration using a static circulation experimental rig at the temperature of 850 °C and oxygen pressure of 1 kPa. Oxides of La.sub.0.7A.sub.0.3MnO.sub.3±delta with different dopant at one level of doping were considered. Rates of elementary acts of the oxygen exchange were found to change differently. So, the oxygen dissociative adsorption rate increased, the oxygen incorporation rate decreased, and the increase in the cation radius did not influence the interphase exchange rate. These trends are associated with the AO segregation processes at the surface and the appropriate mechanism of oxygen reduction is considered. Graphical The oxygen dissociative adsorption rate increased, the incorporation rate decreased, and the increase in the cation radius did not influence the interphase exchange rate. These trends are associated with the AO segregation processes at the surface.