The paper analyses the results of a survey carried on with 200 Peruvian and Bolivian migrants in four cities of Northern Chile: Arica, Iquique, Antofagasta and Calama. After a brief introduction on the historical construction of the borders and social mobility in these territories, the research central categories and the methodology applied (as well as the general profile of respondents) are characterized. The way the respondents build their migrants nets is explained, also defining the function of these nets to the development of a social capital. The temporality of the displacements and the subjects' expectations of geographical permanence and mobility are debated. The discussion highlights how the intensification of the migration to Northern Chile is a result of the migrant circuits which interconnects Peru, Chile, Bolivia and Argentina. Finally some key concepts that articulate the theoretical and empirical information debated are detailed.