The surface tension and density for twelve Cu-Pb-Fe alloys were determined by sessile drop method. The X-ray radiographic technique was used to obtain images of Cu-Pb-Fe drops, and computer programs were employed to calculate densities and surface tensions of investigated alloys. Investigated alloys were selected to cover the composition of reduced alloys from slag obtained during direct-to-blister flash smelting process. The surface tension was found to increase with temperature. It suggests that lead atoms were replaced by iron and copper atoms in the surface phase of the Cu-Pb-Fe alloys.