Most of the arable soils in Northeast Thailand are sandy, acidic and infertile. Their primary and secondary minerals are mainly quartz and kaolinite, respectively. This is because their parent materials are highly weathered. These infertile soils are liable to be degraded by human activities. In this sense, these soils can be said to be typical tropical sandy soils. This paper discusses the characteristics and amelioration strategies of these soils mainly based on the research results of Agricultural Development Research Center in Northeast Thailand (ADRC), a project of Japan International Cooperation Agency