Density and surface tension of liquid Ni -Cu -Fe alloys have been measured over a wide temperature range, including the undercooled regime. A non-contact technique was used, consisting of an electromagnetic levitator, an optical densitometer, and an oscillating drop tensiometer. At temperatures above and below the liquidus point, density and surface tension are linear functions of temperature. The concentration dependence of the density is significantly influenced by a third-order (ternary) parameter in the volume, while the surface tensions can be derived from the thermodynamic potentials (E)G of the binary phases alone.