Glaze-decorated pottery of the Classic Period from the Rio Grande Valley and environs was analyzed using a scanning electron microscope with an X-ray fluorescence detector (SEM-XRF). Cluster analysis of element composition data obtained on the decoration and slip of 57 sherds indicated that intrusive wares could be identified, that trading patterns could be elucidated and that a source of glaze components appears to have located near the Cerrillos Mining district of New Mexico.