This paper considers the problem of raising the efficiency of the initial stage in the processing of copper electrolysis slimes – i. e. oxidation leaching of copper. Metallic copper is the main component of such slime. The overall concentration of elemental and chalcogenide copper in slime at different sites can reach 20 to 30%. Selective leaching (with maximum possible recovery) of copper at the initial stage helps to significantly reduce the amount of slime and makes it easier to recover noble metals, selenium and tellurium. The paper demonstrates the advantages and disadvantages of some known and practiced decopperization techniques, such as aeration low-temperature, autoclave, electrochemical and alternating current decopperization, as well as nitrite process and sulphatization. In order to intensify the long and costly process, it is proposed to use a leaching system that contains a solution of sulphuric acid and hydrogen peroxide as an oxidant. The paper describes the thermodynamic indicators of possible transformations in the metallic copper – sulphuric acid system with different oxidants used, which are applicable at copper electrolysis plants. The paper examines certain features related to the preparation and application of sulphuric acid-and hydrogen peroxide-based leaching solutions, which enable to achieve maximum utilization of peroxide. In order to achieve maximum decopperizing efficiency of the reagent, it is proposed to prepare a mixture of concentrated sulphuric acid and hydrogen peroxide and intro-duce the forming metasulphuric acid in the process at low temperature. The paper describes the outcomes of experiments that aimed at analyzing the aggre-gated indicators of decopperization of a private sample of copper electrolysis slime in the presence of hydrogen peroxide. It was established that when the proposed leaching system is used at room temperature the decopperization degree can reach 90 to 92 % in 30 to 45 minutes.