Liquid alloys of (gadolinium-germanium-manganese) have been studied by a high-temperature mixing calorimetry at (T = 1830) K. The measurements have been performed along five sections with x(Ge):x(Mn) = 0.25:0.75, 0.4:0.6, 0.5:0.5, 0.7:0.3, and 0.8:0.2 for 0.0 < X-Gd < 0.55. The integral enthalpy of mixing (Delta H-mix) has been calculated from the experimental Delta(mix)(H) over bar (Gd) by Darken's equation. The values of Delta H-mix have been also estimated using nine geometric models and the results of Muggianu model implementation provide the best agreement with the experimental data. Two interpolation methods have been used for describing the integral enthalpy of mixing in the ternary liquid alloys. The Delta H-mix values estimated by the interpolation methods agree as well with each other as with the Muggianu model prediction. The differences between the Delta H-mix values determined by experiment and from the model are small and vary from (-4.2 up to 3.5) kJ . mol(-1), which is evidence for a negligibly small ternary interaction in liquid (Gd-Ge-Mn) alloys. Extreme Delta H-mix values are observed in the boundary (Gd-Ge) system. Consequently, the interaction between Ge and Gd atoms make a major contribution to the thermodynamics of liquid (Gd-Ge-Mn) alloys. (C) 2005 Elsevier Ltd. All rights reserved.