Temperature dependence of heat capacity of the La2Zr2O7, Nd2Zr2O7, Sm2Zr2O7 and LaYO3 is measured in the temperature range of 298.15-1373 K by differential scanning calorimetry (DSC). The enthalpy of formation from oxides for LaYO3 was measured by high-temperature lead borate solution calorimetry using transposed temperature drop method. Transformations in the LaYO3 were experimentally studied using differential thermal analysis (DTA) up to 2173 K. The obtained results for heat capacity and enthalpy of formation of the LaYO3 and temperatures of transformations were used to re-optimize thermodynamic parameters of the La2O3-Y2O3 system. (C) 2011 Elsevier B.V. All rights reserved.