Scanning electron microscopy and energy dispersive X-ray microanalysis have been used to examine a representative set of pottery samples from three Celtiberian archaeological sites located in the Upper Duero Valley (Spain), in order to ascertain the technology in their manufacture defined by the type of clay and firing procedures employed. The identification of the use of different types of clay and different firing procedures has allowed the recognition of a highly specialized and diversified level of technological development that might relate to the advance of the Romanization process in this area. The analyses have been carried out with or without conductive coating, in order to define which of the two procedures is more accurate in determining the chemical composition of this type of pottery.