Major parameters of the first stage of leaching of a copper-zinc sulfide product by a culture of Thiobacillus ferrooxidans have been studied, including the effects of solid phase concentration, Fe2+ and Fe3+ ions, pH, and the intensity of mixing. The first stage of leaching of the sulfide raw material is optimum under the following conditions: pH of the original leaching solution equal to 1.6; Fe3+ concentration of order of 10 g/l; and vigorous mixing of the suspension at solid phase concentrations of 30-35%. A theoretical substantiation of the observed dependences is proposed.