Investigations at the Ramaditas site (Guatacondo Valley, northern Chile) were successful in the discovery of small quantities of ancient metallurgical slag, copper ore, and metal from sealed archaeological contexts dating to the first centuries B. C., and in the discovery of adjacent off-site furnace ruins that appear to be contemporaneous. Laboratory tests are positive in identifying both the surface and subsurface slag as a copper smelting by-product. These results are significant in that they demonstrate that copper smelting and metal manufacture were taking place in the Atacama in antiquity, constituting the first conclusive proof of what many Chilean scholars have anticipated since the early 1970s. These results support the view that the mining of minerals and the winning of metals played a valuable role in the economy of the first sedentary villages of interior Chile, in the foothills and valleys that rim the Atacama desert.