The standard molar Gibbs free energies of formation of BaZrO3, and Ba2ZrO4 have been determined by solid-state galvanic cells involving a single crystal CaF2 as a solid-state electrolyte. The e.m.f. measurements were performed in the temperature range (1073 to 1273) K. The average values of the standard molar enthalpy and the standard molar entropy of formation in the temperature range covered by the e.m.f. measurements have been also estimated. The results have been compared with those obtained by other authors. (C) 2007 Elsevier Ltd. All rights reserved.