The purpose of this study is to examine the determinants of internal migration in Thailand in general and the Northeast region in particular. At macro level, the determinants of migration are examined through regression analysis using the 1990 census data. It is found that the most significant variable determining all various migration streams, which are of interest of this study, is migrant stock. This indicates that relatives and friends in the destination areas have a strong influence on migrants' decisions to migrate. The focus of this study is migration from Northeast Thailand to Bangkok. The magnitude of these movements have long been recognised by planners and policy makers and attempts to stem and divert these flows. Such attempts have been made looking at migration in a negative way. However, it is evident that little is known of the actual consequences of rural-urban migration. Planners and policy makers, in designing the more effective policies to modify migration flows, need to have an understanding of the impact of rural-urban migration both on areas of origin and destination. In examining the determinants of migration this study conducted an analysis of the migration process and the impacts of migration on individuals, households and origin communities. It was necessary to conduct research on both origin and destination areas to explore and establish linkages between the broader structural forces and the forces which operate at the individual level influencing decisions to move or stay. Two groups of villages in Roi Et, varying in degree of mobility, were selected for the rural surveys. The urban surveys were conducted in Bangkok. The main findings of these surveys revealed that differences between villages in the incidence of migration are seen to be linked primarily to access to cash cropping and income earning opportunities in the villages. The networks of contacts that build up over time between individuals, households and communities in the rural areas and migrants in Bangkok are the most important factor in the decision to migrate. Evidence from the surveys indicate that migration yields substantial benefits to individual migrants and their households and, at the same time, have a positive impact on the origin communities. The villagers in the study villages perceive migration to be a way by which they can earn more income and improve their standard of living. Migrants in Bangkok maintain strong ties with their households and villages. In this context, circulation, or temporary migration, from the rural Northeast to Bangkok is quite likely to increase. Rural-urban migration needs to be looked at not in terms of the cause of urban problems, but rather as a result of urban growth. The impact of rural-urban migration needs to be further explored and must be taken into account in designing population and development policies. These policies should not only aim at alleviating urban problems but also to recognise and meet the needs of the rural populations.