Based on the study of the kinetics of leaching of copper concentrates by nitric acid, the limiting stages, reaction rate constants, activation energies, and general and partial orders of reactions of the components involved have been determined. An effect of films of reaction products on the limiting stage of the leaching of sulfides by nitric acid has been revealed. It has been shown that in the case of high oxidation potentials no films of elementary sulfur and iron oxide are formed, and the rate of the process is controlled by external diffusion.