This paper examines how an area's development milieu affects the various components of the migration process. After reviewing the literature on migration-development interrelationships, we employ conventional statistical modeling to understand movement among Costa Rican cantons during a five-year period . This is done for the country as a whole, enabling cross-national comparisons with earlier studies, and for urban-to-urban, urban-to-rural, rural-to-urban, and rural-to-rural streams, which are compared with one another. The results indicate that the models describe urbanbased migrations better than rural-based ones; variables closely associated with the market economy have a weaker role in rural settings: and push factors of migration are as important as pull factors. Finally, the spatial pattern of variation in migration processes is consistent with core-periphery development models and with earlier observations of an urban bias in Third World research.