We discuss novel electrochemical data on Bi2Sr2CaCu2O8+δ(BSCCO) at high temperature, where equilibrium with the oxygen containing neighboring phase is established. Measurements of the electronic conductivity as a function of oxygen partial pressure and temperature convey information about the defect chemistry. Careful investigation of the electrochemical polarization on glass-sealed cells allows the determination of the ionic conductivity. The investigation of the instationary response of the electrochemical polarization measurements enables us to determine the chemical diffusion coefficients.