The kinetics of pyrite oxidation in potassium dichromate solution was investigated. The effect of stirring rate, temperature and particle size have been examined. In addition the solid phases before and after leaching were examined by SEM, electron microprobe and chemical analysis. The rate of pyrite oxidation was found to be independent of the stirring speed. The consumption of dichromate ions in the initial solutions showed that at all temperatures under consideration sulphide sulphur was oxidized to sulphate. The value of the apparent activation energy of 43.5 ± 1.5 kJmol^-1, the independence of reaction rate on the stirring speed, the linear relationship between the rate constant, and the inverse of the initial particle diameter are in good agreement with a mechanism controlled by chemical reaction.