By "Kunten-shiryō (punctuation materials)" are meant any Chinese writings with kana (the Japanese syllabary) and other symbols glossed between, the lines so as to facilitate reading Chinese characters as rendered. into Japanese. The materials of this kind since the ninth century are abundantly extant in ancient temples. Their language is strongly traditional, but the medieval kunten-shiryō written from the twelfth through the fifteenth centuries reflect new phonemes, vocabulary, and diction during this period. Consequently, they provide us with materials for the study of medieval Japanese. The present study proposes to elucidate the actual conditions and characteristics of medieval Japanese, with special reference to the kunten-shiryō in eleven different texts of Ku-wên-hsiao-ching (古文孝経).