The overall objectives of the proposed research are to explore the various dimensions and determinants of health status change among young adults (age 15-29) resulting from migration from rural areas to urban areas;and to explore the relationship between health status and subsequent decisions to migrate, i.e., migration selectivity. The specific aims of the proposed research are to provide a multidimensional assessment of young adult health for migrants and for non-migrants in sending areas (rural Kanchanaburi Province, Thailand), and receiving areas (Kanchanaburi and Bangkok metropolitan areas);to provide an assessment of changes in various dimensions of health status over time for both migrants and non-migrants;and to provide an assessment of the degree to which differences between the health of migrants and non-migrants are due to migration processes per se, to contextual factors in both rural and urban environments, to family-level factors related to affluence, and to a priori individual differences related both to decisions to migrate and to various dimensions of health status (selection factors). These objectives and aims will be accomplished by adding a longitudinal health study to an ongoing demographic research project in Kanachanaburi province, Thailand. Data from the proposed health study will be linked with the individual, family, and contextual data collected by the existing project. The research design consists of 3 waves of data collection, and a comparison of changes of health status over time among rural non-migrants;urban non-migrants;and individuals who were rural residents at baseline who subsequently migrate to urban centers by the second or third wave of data collection.