Development of a Mine in Andes Mountains, Peru by Yumisaburo NURAI The development of Huanzala Mine was started in October 1966 after the completion of prospecting and production began at 500M.T./day crude ore one and a half year later. At present, the mine is milling 850M. T. /day ore steadly and will increase the production to 1,050 tons of ore a day in near future. This development has the following characteristics ; (1) As a result of minimizing the equipment and simplifying the system of the plant, the total investment covering from the initial stage to 1, 050M. T. /day construction works was almost as the same as in Japan, in spite of the fact that freights and import-export charges amounted to 80% of the purchase price of the equipment. (2) The appropriate exploration based upon geological study of the Huanzala formation has brought about increased ore reserves. The proper selection of mining methods based on sufficient experience in Japan has made the operation stable. (3) The flotation process was improved so as to be suitable at high altitudes. This improved concentrator is now operating for the treatment of complex ore with the productivity equal to that of Japan, in terms of operating costs and performances. The above-mentioned success in the operation has brought about the following effects; (1) Peruvian Government and the regional community placed reliance upon our technology. As a result, the technological exchange between Japan and Peru has been prompted, and many new mines and claims have been offered for development. (2) The valuable data and experiences obtained at high altitude of 4,000m and in the isolated village away from the industrialized areas, will serve as a good reference in the development of overseas mines which would be attempted in the future.