Phase equilibria in the Au-Ge-Ni ternary system were studied by means of scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. The phase relations in the solid state at 600 A degrees C as well as a vertical section at Au72Ge28-Ni were established. No ternary compound was found at 600 A degrees C. On the basis of the experimental phase equilibria data, a thermodynamic model of the Au-Ge-Ni ternary system was developed using the CALPHAD method. Thermodynamically calculated phase diagrams are shown at 600 A degrees C, in two vertical sections and the liquidus projection. Reasonable agreement between the calculations and the experimental results was achieved.