The kinetics of oxygen transport in La0.5Sr0.5CoO3-delta were investigated using the electrical conductivity relaxation technique in the temperature range from 600 degreesC to 700 degreesC and with oxygen partial pressures from 0.01 to 1.0 atm. The effects of oxygen partial pressure on the chemical diffusivity of oxygen, D-chem, and surface exchange coefficient, k(chem), were investigated by systematically changing the initial (p(1)) and the final (p(2)) oxygen partial pressures. Results showed that for oxygen partial pressure switches with p(1)/p(2) > 20, a linear model for the exchange kinetics is no longer valid. The dependence of the exchange kinetics on the final oxygen partial pressure was determined.