The present Paper has two main objectives---the first is to make an inquiry into the problem of the reasons why, unlike in the case of most alluvial plains in Japan, the ratio of paddy fields to cultivated land is small in the Tenryu alluvial plain, and also to study the type of land use which is prevalent there; the second is to make an investigation of the progress made since the Meiji Restoration in the retarded development of the Mikatahara Tableland, which is an elevated fan lying to the west of this alluvial plain.<br>In the first place, the present writer has tried to clarify the distribution pattern of the paddy fields and upland fields in the alluvial plain, and he has taken special note of the wide distribution of the peculiar butte-like upland fields. The upstream region of this alluvial plain constitutes a fan, while the downstream region forms a delta. As there is a complex distribution of former river courses, natural levees, flood plain swales, flood plain bars, etc., in the delta region, the land surface abounds in microrelief. The irrigation water for the paddy fields in this alluvial plain is supplied by the irrigation canals leading from the mouth of the gorge of the Tenryu River. However, because of the low water-level of the Tenryu River, the water-level of the irrigation canal is likewise low; in addition to this, the slope of the plain surface is extremely gradual, so that in the days when pumps were unknown, it was impossible to supply water to parts of the plain that were even only slightly elevated. Thus, the present pattern of land use which resulted from these circumstances dates back to old time. In order to obtain an income from upland field crops, the cultivating farmers cultivated sweet potatoes, wheat, and barley, to which were added cotton, indigo-plant, mulberry, sponge-gourd, peanuts, melons, and other commercial crops which were raised in accordance with the vicissitudes of the times.<br>The Mikatahara Tableland is located at an elevation. Hence, it was difficult to procure water from the Tenryu River. Moreover, as the ground water is deep, drinking water was not easily obtainable, the result being that almost the whole of the tableland remained unreclaimed even until as late as the Edo Period (1603-1867). This unreclaimed land was utilized by the cultivating farmers dwelling in the lower regions as source for the grass used in the production of compost. In the Meiji Period (1868-1912), portions of this land were developed by members of the warrior class who had become cultivating farmers, but for the most part, the land became a crown holding. In the latter half of the period of crown holding, approximately half of the land was reclaimed by cultivating farmers of the neighborhood to whom it was loaned. In time, the extensive areas left uncultivated became military grounds. After the Second World War, most of the military grounds were released for development as upland field land. Later, however, plans were altered, and ultimately, as part of the project for the multiple development of the Tenryu River, modern develoment plans were made for the making of paddy fields by supplying water by means of a large irrigation canal from the large-scale dam constructed in the Tenryu River. Work on this project is currently under way.