132 clay and Roman pottery samples were collected from various kiln sites, settlement sites and clay outcrops in the Lower Nene Valley, Eastern England. 23 elemental concentrations were determined for each sample using inductively coupled plasma emission spectrometry. The pottery sampled is divided into four groups on the basis of the results, and it is suggested that each of these groups represents material made from a separate clay. The likely sources of these four clays are identified. One of the clays appears to have been used over a period of approximately one and a half centuries to make a variety of pottery types at several kiln sites. In addition, it is probable that this same clay was mixed prior to use. The effect of levigation and firing on the clay samples' chemical compositions was also investigated. Both were found to have a marked effect of about the same magnitude; firing had a fairly uniform effect on the elemental concentrations, whereas levigation did not. -- AATA