Archaeological fieldwork in the Batán Grande Archaeological Complex on the north coast of Peru has produced evidence of metallurgical activity in the pre-Hispanic period spanning at least 500 years, from 1000 A.D., involving an industrial scale and a prill extraction copper smelting process. Prills are copper droplets formed in unwanted slag residue as the ore is reduced. Detailed description is included of construction and organization of the smelting furnace. Radiocarbon dating was carried out on charcoal from the furnaces. Preliminary results of proton-induced x-ray emission analysis of the prills indicate that arsenic-bearing compounds are included in the initial smelt. This newly documented technology evolved locally from at least 800-900 A. D., and supports the claim of Andean metallurgy to be a major cultural tradition. -- AATA