The Ag-Ge binary system has been assessed thermodynamically using the CALPHAD method through the Thermo-calc (R) software based on the available experimental information from the published literature. The solution phases including liquid, fcc_A1(Au,Ag), and diamond_A4(Ge), were modeled as substitutional solutions and their excess Gibbs energies were expressed by the Redlich-Kister polynomial. On the basis of the previous assessments of the Au-Ag and Au-Ge binary systems, the thermodynamic description of the Au-Ag-Ge ternary system has been performed. The liquidus projection and several vertical sections of this ternary system have been calculated, which are in good agreement with the reported experimental data. (C) 2010 Elsevier B.V. All rights reserved.