The kinetics of pyrite oxidation in perchloric acid solutions were investigated at temperatures ranging from 30degreesC to 40degreesC, potassium dichromate concentration from 0.001 to 0.05 mol L-1, particle size fractions from 50 to 150 mum and pH values down to 2.83. The rate of the oxidation reaction is described by the following expression: r = bkS(0.51)[K2Cr2O7](0.64)[H+](0.22) where S is the surface area of reacting solid, r represents the amount of Fe release in solution per unit surface area per unit time, b is a stoichiometric factor, k is the rate constant, and [K2Cr2O7] and [H+] are the potassium dichromate and hydrogen ion concentrations respectively. The magnitude of the activation energy (74.83 kJ mol(-1)) and the direct relationship between the rate constant and initial pyrite specific surface area are in agreement with a mechanism controlled by a chemical reaction. Trace element content had no statistically significant effect on the oxidation rate.