The proposed study will examine a number of health outcomes among Vietnamese living both in the United States and in Vietnam. A major substantive focus will be the investigation of overall health status and core health beliefs among working-age Vietnamese adults who have recently immigrated to the United States. Key dimensions of health to be exposed include physical functioning, role limitations, pain, social functioning, general mental health, stress, vitality, energy, fatigue, and general health perceptions. While there is an extensive literature on the health of other major immigrant groups, we know much less about the health of Vietnamese Americans, who constitute one of the largest waves of immigration to the United States in recent history. A major methodological focus will involve the development of new techniques to better explain health differences between migrants and non-migrants. Attributing reported effects of migration on health to specific causes are complicated by the inherent difficulties of separating the effects of migration per se from selection factors. If migrants are not representative of sending populations, then differences between migrants and non-migrants in the sending countries are difficult to interpret. Our approach to separating migration effects from selection effects involves a "natural" experiment that compares three distinct groups: Vietnamese immigrants in the United States; Vietnamese who have never left Vietnam; and Vietnamese returnees in Vietnam.