Partial and integral enthalpies of mixing of liquid Bi-Ni alloys were determined at 1273 K, while enthalpies of mixing of ternary Ag-Bi-Ni alloys were determined at 1173 K over a broad composition range along six sections: x(Ag)/x(Bi) = 3/2, 1, 2/3, 3/7, 1/4; x(Bi)/x(Ni) = 4. Measurements were carried out using Calvet type microcalorimeters and drop calorimetric technique. It was found that integral enthalpies of mixing of binary Bi-Ni alloys are small exothermic, whereas integral mixing enthalpies of ternary Ag-Bi-Ni alloys change sign from negative to positive with decreasing Bi content. The ternary data were fitted on the basis of an extended Redlich-Kister-Muggianu model for substitutional solutions, and additional ternary interaction parameters were determined. From experimental ternary data the range of liquid at 1173 K was deduced.