THIS CHAPTER CONSIDERS SOME IMPLICATIONS OF THE DEMOGRAPHIC CHARACTERISTICS OF THE HIGHLANDERS. IT FIRST SKETCHES THE CHARACTERISTICS OF HIGHLAND POPULATIONS: SIZE, LANGUAGE GROUPS, DISTRIBUTION, AGE-SEX STRUCTURE, DEPENDENCY RATIO, VITAL RATES, THAI LANGUAGE ABILITY AND LITERACY, AND OPIUM ADDICTION. IT THEN DISCUSSES FACTORS AFFECTING MIGRATION, MORTALITY, AND FERTILITY. THEN IT CONSIDERS THE RELATIONSHIP BETWEEN TWO BASIC ECONOMIC TYPES (SUBSISTENCE FARMING AND CASH CROPPING) AND POPULATION CHARACTERISTICS OF TWO GROUPS, LUA AND HMONG (MEO), WHICH REPRESENT THESE ECONOMIC TYPES. IN CONCLUSION IT SUGGESTS THAT RAPID POPULATION GROWTH WILL BE AN INCREASING PROBLEM IN THE NORTHERN THAI HIGHLANDS, WHICH WILL HAVE IMPORTANT CONSEQUENCES IN THE LOWLANDS AS WELL.