This piece of research seeks to highlight and test a series of models for social, political, economic and settlement change in southern Mesoamerica. Based on recent studies in the area (1995-97) Francisco Belli outlines the theoretical premises and methodology of his research, using GIS to elucidate changing patterns of population and settlement growth and decline, changing economic strategies, social organisation and administration. This volume contains material (settlements, site plans, stratigraphical information, details on settlement organisation, art, architecture and trade patterns) from the Preclassic, Classic and Postclassic periods, used to test diffusionist versus indigenous models for the development of societies.