Archaeological investigations on the margins of high civilizations have traditionally been guided by the assumption that polities in such zones were peripheral to core states. This paper argues that this assumption obscures the multiple dimensions along which core/periphery distinctions can be measured and ignores the possibility of mutual influence and interdependence among interacting societies at all size and complexity levels. This confusion is particularly evident in the study of southeastern Mesoamerica (adjoining portions of Guatemala, Honduras, and El Salvador), usually viewed as peripheral to lowland Maya core states during the Late Classic period (A.D. 600-950). In an attempt to advance the study of polities bordering complex and extensive sociopolitical systems, a general model is outlined which sets out to identify the different dimensions of peripherality and specify the conditions under which various sorts of core/periphery relations are likely to develop. Late Classic political, economic, demographic, and cultural patterns from the Naco Valley, northwestern Honduras, are then examined to determine how this area was linked to lowland Maya core states (represented here by Copan and Quirigua) and what effects these ties had on indigenous developments. The essay concludes with an overview of Late Classic lowland Maya/non-Maya interactions in the Southeast and some general suggestions for future research.