Bronze production during the Iron Age of the Iberian Peninsula is characterised by the use of a relatively simple technology, based on crucible-furnaces. In an area rich in mineral resources, bronze was produced on a small scale and within settlements, to be used for ritual, ornamental and functional objects. Here we present an analytical study of slagged crucibles, small slag nodules and casting spillage from the Iron Age hillfort of El Castru, in Vigaña (Asturias, NW Iberia), with a particular focus on the technology of bronze production. The study sought to contribute to our understanding of Pre-Roman metallurgical activities in the region, as a case in point to discuss broader prehistoric traditions of bronze-making. The results show that the technology and scale of bronze production at this hillfort are coherent with the pattern described for much of prehistoric metallurgy in Iberia, with the-direct production of copper alloys by cementation and co-smelting of mineral ores. The results also illustrate some of the challenges encountered when attempting to identify metallurgical processes through the analyses of crucible residues, and propose some criteria to facilitate future studies.