Purpose. Substantiation of an economically feasible method for developing the Kusmuryn deposit. Methodology. Analysis of literature and stock materials; studying physical and mechanical properties of rocks and ores. Findings. To improve economic performance and to reduce the cost of concentrate at the Kusmuryn deposit, the mining system is being changed. To replace the chamber-and-pillar development system, which allows extracting all the available reserves, a more effective model was introduced: development of inter-chamber pillars with a high metal content. The authors proved the expediency of development by the open method using the development system with horizontal layers with the goaf stowing. Originality. Calculating the technical and economic indicators of the three mining options allowed selecting the most effective mining method at the Kusmuryn deposit. In order to prevent underground fires, a layer caving system with siltation of crushed rocks is recommended. For disseminated ores, the usual method with collapsing overlying rocks is applicable. Practical value. Based on the studies, recommendations were developed for the Kazakhmys Corporation. They are referred to reducing the open pit mining at the Kusmuryn field in 2019. This stabilizes the achieved production level and compensates for retiring functioning facilities associated with the field. The introduction of underground mining is recommended from 2021.