The desulphurization of a carbon-saturated Fe-Si-S alloy by CaO and CaO-7.5% CaCl2 slags at 1300 degreesC, and by CaO-10% CaF2 and CaO-7.5% CaCl2 slags at 1450 degreesC were investigated. The results indicated that the addition of 7.5% CaCl2 to CaO improved the desulphurization of the carbon-saturated Fe-Si-S alloy at 1300 degreesC by forming a liquid reaction surface. X-ray diffraction studies on the reaction surface of CaO showed that solid CaS formed on the lime surface. This solid reaction product reduces the transfer of sulfur to the CaO surface. At 1450 degreesC, CaO-10% QaF(2) and CaO-7.5% CaCl2 slags contain both liquid and solid phases. X-ray diffraction studies showed that a smaller amount of solid CaS formed on the reaction surface of the CaO-7.5% CaCl2 slag than on the CaO-10% CaF2 slag. The formation of a smaller amount of solid CaS and the presence of a liquid phase at the metal-slag interface enhanced the desulphurization with CaO-7.5% CaCl2 at 1450 degreesC.