The enthalpies of mixing of liquid Ni-Ti-Zr alloys were determined at 1873 K by means of a high temperature isoperibolic calorimeter. The investigations were performed along sections chi(Ni)/chi(Ti), = 4/1 and chi(Ni)/chi(zr) =4/1 in the corresponding composition ranges chi(zr) = 0-0.41 and chi(Ti), = 0-0.48. The limiting partial enthalpy of mixing of undercooled liquid zirconium in liquid Ni-Ti alloy is (-192 +/- 8) kJ mol(-1). The limiting partial enthalpy of mixing of undercooled liquid titanium in liquid Ni-Zr alloy is (-130 +/- 12) kJ mol(-1). The integral mixing enthalpies are negative over the investigated composition range. An analytical expression for the representation of the integral mixing enthalpy was obtained and used for the calculation of the function in the whole composition range. (C) 2016 Elsevier Ltd.