The partial yttrium (Delta(mix)(H) over bar (Y)) and the integral (Delta H-mix) enthalpies of mixing of liquid ternary Al-Ga-Y alloys have been determined by high-temperature mixing calorimetry at T = 1750 K. The measurements have been performed along five sections with constant ratios of Al and Ga in a range of 0.0 < x(Y) < 0.64. The Delta H-mix has been estimated in the ternary system using asymmetric geometric models and the Toop model has been chosen as the most adequate one. The deviation between experimental and that predicted by the geometric model values of Delta H-mix was found to be 1.54%, so ternary interaction is negligibly small at the experimental temperature. The possible contribution of binary intermetallide compounds into the thermodynamics of the liquid Al-Ga-Y alloys is discussed. (c) 2005 Published by Elsevier Ltd.