The leaching kinetics of sphalerite with pyrite, in water saturated in chlorine, has been investigated. The leaching rate of sphalerite and pyrite increased with decreasing particle size, and with increasing stirring rate and gas flow rate. Increase of reaction temperature caused the leaching rate of sphalerite to increase, and that of pyrite to increase in the temperature range of 12-20 degrees C and to decrease in the temperature range of 30-70 degrees C. The kinetics and mechanism of dissolution reaction for sphalerite and pyrite were found to be diffusion controlled through the product layer. The activation energy for sphalerite in the ore was calculated as 22.68 kj mol(-1). The activation energies for pyrite were calculated as 43.28 kj mol(-1) in the temperature range 12-20 degrees C and 8.37 kj mol(-1) in the temperature range 30-60 degrees C.