The kinetics of the carbothermic reduction of zinc sulfide in the presence of calcium oxide has been investigated by atomic absorption spectroscopy (AAS) and thermogravimetric analysis system (TGA). Experimental results indicated that the rate of zinc yield could be increased by increasing the argon flow rate, the reaction temperature, the initial molar ratio of C/ZnS, or the initial molar ratio of CaO/ZnS. Furthermore, the rate was also found to increase with decrease in the sample height, the size of carbon aggregate or the initial bulk density. Based on these experimental data, an empirical rate equation of zinc yield has been formulated. (c) 2007 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.