The increase of the population is particulary evident in the tropics and subtropics, and it is anticipated that many people will be confronted with food shortage and the deterioration of the environment, including the disappearance of tropical forests and desertification. Expansion of land area for cultivation is needed, but the land area suitable for cultivation is decreasing because of desertification, soil degradation, etc. Therefore, the development of marginal land areas for agriculture in harmony with the regional eco-environments is necessary. The Marginal Land Research Division has carried out fundamental research to enable the exploitation for agriculture of the marginal lands of the tropics and subtropics and to promote sustainable agricultural production. The soil and water resources and climatic analysis of the marginal lands were evaluated as agricultural resources in order to promote the development of techniques for the utilization of such lands for agriculture.