A syndrome of sudden and unexpected death during sleep occurs among adult Southeast Asian refugees in the United States. Surveillance for sudden deaths was conducted among Laotian-Hmong refugees in the Ban Vinai refugee camp in northeastern Thailand to determine if a similar cause of death occurs there. Sixteen sudden and unexpected deaths associated with sleep were found that were similar to the sudden deaths noted among Southeast Asian refugees in the United States. A case-control study in Ban Vinai revealed associations between sudden death in sleep and membership in the Green-Hmong subgroup, a family history of sudden death, and previous non-fatal sleep disturbances. Sudden and unexpected death during sleep of young adults is a regional phenomenon within Asia and occurs in populations that are culturally and genetically distinct. Migrants from affected populations in Asia carry with them the susceptibility to sudden death in sleep.