The phase diagram of the system LiF-LuF3 has been revised using thermal analysis. Specific heat capacity and enthalpy of phase transition and fusion were measured by differential scanning calorimetry for all compounds belonging to the system. A thermodynamic optimization of the LiF-LuF3 phase diagram was performed by fitting the Gibbs energy functions to the experimental data that were taken from the literature or measured in this work. Excess energy terms, which describe the effect of interaction between the two fluoride compounds in the liquid solution, were expressed by the Redlich-Kister polynomial function. The assessed phase diagram was in suitable agreement with the re-evaluated experimental data. (c) 2012 Elsevier B.V. All rights reserved.