Experimental data are presented for the solubility of sulfur in liquid Fe-C alloys coexistent with solid calcium oxide, calcium sulfide and carbon monoxide of known pressures at 1 600°C. The equilibrium constant is determined for the sulfur reaction in terms of the activities of sulfur and carbon in iron for composition ranges 0.005 to 0.4% S and up to 3% C. The extrapolation of the data to hot metal compositions predicts for unit activities of calcium oxide, calcium sulfide and carbon monoxide, the equilibrium sulfur content of 4ppm for 1 600°C and 8ppm for 1 400°C. In relation to ladle desulfurization of hot metal, selected data are presented on some slag-metal reaction equilibria.