In the past ten years a good deal of literature has been written on the subject of internal migration. Demographers and sociologists in particular, have made a significant contribution to knowledge on diverse aspects of this many-sided phenomenon; the former, by devoting preferential attention to methods for the obtainment of data, to techniques for the measurement of intensity, to the quantitative analysis of demographic variables, and to the formulation of mathematical models of the process. In their turn, sociologists have focused their attention on the search for explanations of the phenomenon, nearly always with reference to concrete "social problems"?those occasioned by rapid urbanization?selectivity, social mobility, and assimilation, with all their implications. Demographers have made intensive use of census data and naturally treat migratory movements as a fundamental variable?together with natality and mortality?of spatial redistribution of the population and of changes in the demographic structure of the different geographic segments (urban-rural, regions, etc.) of a country. There have also been studies which have attempted to link this process with economic develop? ment (for example, industrialization), or with more specific aspects such as the utilization of human resources, and housing needs; and with social changes, particularly those influencing the level of fertility. As a rule, sociologists have carried out much more localized investiga? tions, both from a geographical point of view and from that of subjects covered, and therefore, of greater depth than scope. These studies have This paper was presented as the background document to the Latin American Regional