This article is an attempt to identify the urban structure built on the historical evolution of the economic basis of cities which conform the Great Concepcion and their dimensions, levels and patterns of spatial interaction. Using the data of the Passengers Origin-Destination Enquiry (1970), the functional complementarities of the urban space (Labour-Housing Budget Index) and globaland specific fluxes of alternant migrations are set up.The functional structure of the Great Concepcion is characterized by a clear concentrated pattern of employment and educational opportunities, where Concepcion is the focus'of terciary sector and Talcahuano the attractive industrial core. Other metropolitan cities, without any functional basis to support labour, are declining their satellite roles. The social structure is strongly associated to this pattern, resulting extreme ecological differences.Spatial complementarities produce large commuting, with a centripetal relationship at Concepcion-Talcahuano and from the rest of the cities to this Metropolitan core.Summarizing, the historical development has created large employment, social and growth inequalities, which are acting as circular acumulative factors of the concentration process. Finally, the author reviews the urban development options from a neccesary planning process.