Jori System is a land system concerning the adjustment of partitions of agricultural land in the ancient times of Japan, and is one of the most principal elements showing phases of that time. The theme I have taken up here in this paper is how this system was applied on the Ado river delta-fan, Takashimagun (Takashima county, Shiga Pref. at present). Fig. 6 shows the locations of “Jo” and “Ri” in this area which I have restored with the help of some historic records of the Middle Ages.<br>These are summings-up:<br>1) The traces of this system still remains clearly in the area surrounded by the two diluvial uplands, Aebano and Taizanjino. However few traces are to be seen in the area along the basins of the Ado river and the Kamo river, or on the old river channels, the lagoons and the backswamps where there occurred frequent floods or submergence of rivers and lakes.<br>2) According to this system, the land was divided along the two different directions: in the south it was divided along the north-south line of N16°E, covering the whole area of the alluvial plain, and in the northern part of the plain, along the line of N6°E.<br>3) Kozu monor under the control of the Enryakuji temple was established during the period of 1135∼40, which occupied the northern part of the alluvial plain along the left hand-side bank of the Ado river and the Aebano diluvial upland. The detailed descriptions of the farm land belonging to this monor are given in “Kozusho-Kenchucho” and “Kozusho-Indencho”. Making a comparative study between the historical evidences given in “Kozusho-Indencho” and Fig.1, the following points have become clear: this farm land now lies under the water of Lake Biwa within 2.5m in depth; although the time when it sank under the water is not quite certain, it is supposed to be from the latter half of the 15th century toward the 16th.<br>4) The Jori System seen on the alluvial plain along the downstreams of the Ado river was like this:<br>The “First-Jo” starts at Uchioroshi in Takashima-cho situated on the southern end of the plain, and the “18th-Jo”, the northernmost one, ends at Kozu, in Shinasahi-cho. In regard to “Ri”, however, its starting points on each “Jo” are not on the straight line. Each starts at somewhere around Aebano or at the foot of Taizanjino diluvial upland in the west and disappears into Lake Biwa in the east. This difference seems to have much to do with the geographical features of this area: the gradient of the slope lying in the western part of the plain varies in different places. Fundamentally, the system applied here belongs to Omi-type Jori System: “Jo” was counted toward the direction of “Tsubo-su” and “Ri” toward the direction of “Tsubo-nami”.