One of the most dynamic aspects of socioeconomic change in less-developed countries is expressed by their internal migration patterns. A large percentage of the present urban population in most of these countries has migrated at some time, either from a rural environment or from another city. In the Dominican Republic, over two-thirds of all urban dwellers are migrants. Rural areas, too, are often in flux, with a sizeable percentage of the population either having lived in cities or having moved from other rural areas. In the Dominican Republic, almost one-half of all those residing in the countryside have migrated. Such impressive population mobility, especially the rural-to-urban flow, is probably an inevitable concomitant of the development process as a country's labor force redistributes from the agricultural to the industrial sector [Sahota 1968, p. 218]. Broadly speaking, the phenomena of population shifts present the economist with two distinct, but related problems [Sjaastad 1962, pp. 81-2]. First, is migration a purposeful response of people to their perception of alternative economic conditions and opportunities in different regions of a country?' The second question, which, as Sjaastad notes, is the more difficult of the two, springs from the first: are migration flows effective in reducing the interregional economic disparities that originally generate migration? The present study analyzes individuals by migrant status and interprovincial aggregate migration rates in the Dominican Republic. Within the limitations posed by the available Dominican data, we find considerable evidence that migration flows are strongly affected by economic conditions, both in the area of origin and destination. Moreover, we offer tentative empirical support for the contention that migration helps equalize initial economic differences between regions losing population and regions gaining population. The first part of this study presents estimated urban-to-urban, urban-to-rural, rural-to-urban, and rural-to-rural migra-