The Rosenburg method has been applied to determine physicochemical properties of Cu2O at 900-1000 degrees C and oxygen pressures from 0.005 to 0.1 atm. The defect concentration was proportional to p(O2)(1/4), whereas the defect diffusion coefficient was essentially independent of the ambient oxygen pressure. This is interpreted to reflect that the dominating defect in Cu2O is neutral Cu vacancies. The formation enthalpy of neutral copper vacancies was observed to be approximately 60 kJ/mol and the formation entropy approximately -11 J/mol K. Migration enthalpies and entropies have been calculated from the temperature dependence of the defect diffusion data and are approximately 54 kJ/mol and 5.8 J/mol K, respectively. Combination of the enthalpy of formation and migration of the vacancies yields an enthalpy for Cu self-diffusion in Cu2O of approximately 115 kJ/mol.