Demographic and health conditions among Hmong in Thailand were examined in comparison with other ethnic groups which closely resemble the ethnic origins of Southeast Asian refugees in the U.S. Thailand Hmong have very large extended family households, very high birth rates, low use of contraception, very young age at first marriage, and, compared with other highland minorities, relatively low infant and crude mortality rates. Hmong use of tobacco and alcohol and other stimulants is lower than other ethnic groups, and is much more frequent among men than among women. Opium was used by 15% of the men in the surveyed village, lower than among another highland group, but higher than in surveyed lowland villages. Fewer illnesses were reported by Hmong in the 7 days prior to survey than in other rural groups. Relatively low Hmong morbidity and mortality as compared with other highland ethnic groups may be associated with low use of tobacco and alcohol, and with the sharing of child care responsibilities within the large Hmong extended family households.