The heat capacities of cerium and lanthanum silicates (Ce2Si2O7 and La2Si2O7) were measured from 4 to 400 K by adiabatic calorimetry. The derived thermodynamic functions, {H degrees(T)-H degrees(0}, S degrees and {G degrees-H degrees(0)}/T were calculated. The standard molar entropies at 298.15 K were determined as 220.32+/-0.44 J mol(-1) K-1 and 210.7+/-0.42 J mol(-1) K-1, respectively. Enthalpy increments relative to 298.15 K were measured by drop calorimetry from 500 to 900 K. From these data the thermodynamic functions, including the enthalpy and Gibbs free energy of formation of the two compounds were derived for temperatures up to 1000 K.