The sodium and chromium contents in lead smelting slags are increasing with the increase in waste recycling. The lead solubility in the slag is important from both an economical and environmental perspective. As a fundamental study, experiments have been carried out to determine the equilibria between FeOx-CaO-SiO2-5mass%NaO0.5 or FeOx-CaO-SiO2- 5mass%CrO1.5 slags and lead metal in iron crucibles at 1573K. It has been found that addition of soda decreases the lead solubility in SiO 2 rich side of the slag, while soda increases the solubility in CaO rich side. Chromium in the slag decreases the lead solubility in the FeOx-CaO-SiO2 slag. The activity coefficients of PbO in the FeOx-CaO-SiO2-5mass%NaO0.5 or FeOx-CaO-SiO2- 5mass%CrO1.5 slags were compared with those of the CaO-SiO 2-FeOx ternary system.