Electromotive force (EMF) measurements for various Dy-Ni intermetallic compounds in two-phase coexisting states were carried out in the temperature range of 673-773 K in a molten LiCl-KCl-DyCl3 (0.5 mol%) system. The activities and relative partial molar Gibbs free energies of Dy were obtained from the measured EMFs for various Dy-Ni intermetallic compounds, DyNi2, DyNi3, Dy2Ni7, and DyNi5. The relative partial molar entropies and enthalpies of Dy were also calculated from the temperature dependence of the EMFs. The activities and relative partial molar properties of Ni in the compounds were calculated from the activities of Dy by using Gibbs-Duhem equation. Finally, the standard Gibbs free energies of formation for the Dy-Ni intermetallic compounds were estimated. (C) 2003 Elsevier Science Ltd. All rights reserved.