Oxygen tracer diffusion coefficient (D ⁎ ) and surface exchange coefficient (k ⁎ ) have been measured for (La 0.75 Sr 0.25 ) 0.95 Cr 0.5 Mn 0.5 O 3−δ using isotopic exchange and depth profiling by secondary ion mass spectrometry technique as a function of temperature (700–1000 °C) in dry oxygen and in a water vapour-forming gas mixture. The typical values of D ⁎ under oxidising and reducing conditions at ∼1000 °C are 4×10 −10 cm 2 s −1 and 3×10 −8 cm 2 s −1 respectively, whereas the values of k ⁎ under oxidising and reducing conditions at ∼1000 °C are 5×10 −8 cm s −1 and 4×10 −8 cm s −1 respectively. The apparent activation energies for D ⁎ in oxidising and reducing conditions are 0.8 eV and 1.9 eV respectively.