The major aim of this paper is to answer the following three questions : 1)How really was the Japanese system of Buddhist ordination executed (instituted by Ganjin 鑑真 in the mid-eighth century) especially the Theravada ordination ceremony (kaidan 戒文壇) of Todai-ji 東大寺, carried on during the medieval period? 2)What was the function of this medieval system for the monastic groups of the time? 3)While the conventional opinion is that the ordination system became a dead skelton during the medieval time, what was the relation of this skeltonization process to the revival of the Buddha's teachings and sacerdotal laws carried on by Kakujo 覚盛, Eison 叡尊 and other sedutionalists? The author concludes that : (A)Even during the medieval period, the ordination system retained an important meaning ; and for this reason, while there might have been some postponement and delay over the years, in principle, it was continuously held every year (for Todai-ji during a three day period beginning on the twentieth day of the tenth month) as evidenced by existing ordination certificates (kaicho 戒牒), which were issued at this times. (B)The most fundamental significance of the ordination system lay in the fact that through the holy ceremony novices would become fullfledged, officially recognized monks (kanso 官僧), therefore making the system the sole criterium for membership of the official state ecclesiastics. (C)Many events can be explained as a result of the establishment of a new ordination by Kakujo and Eison, and growth of Sedutionalist monks of Ritsu 律 sect : a typical example, the exclusion by Todai-ji of common born (bonge-bun 凡下分) novices (shami 沙弥) from the ordination ceremony were caused by the reduced number of the clerics who received the ordination. These results, combined with such facts as 1)Mahayana ordinations at Enryaku-ji 延暦寺 functioning much the same way as for Todai-ji, 2)Mahayana and Theravada ordinations being similar in thier relation to the aristocracy -for example, both were administered by the temple synod (Sogo-sho 僧綱所) and also the diplomacy and Buddhism Office (Genba-ryo 玄蕃寮) of the Bureau of Aristocratic Domestic Affairs (Jibu-sho 治部省), and 3)Pure Land sect (both Chinzei 鎮西 and Seizan 西山 factions), Nichiren sect and Zen sect all having their own ordination systems, enable the author to argue that it was the ordination system alone of the medieval period which functioned to unify group of monks. Two clerical categories are proposed : the official monks (kanso). who received authentic duties to pray for the security of the state, which were entrusted by Tenno who was ultimately in charge of state religious ceremonies, and the sedutionist monks (tonzeso 遁僧), who formed permanent religious group who chose not to conform to the criteria laid down for their kanso counterparts. The official monk group were conformed to either the Theravada or Mahayana ordination system ; whether a certain monk was an official cleric or a nonconformist depended on which ordination system he conformed to. It becomes clear that from the later years of the Kamakura period the representative of the religious power in Japan was the tonzeso who embraced Kamakura Reform Buddhism.

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