In the Annals of T'ang dynasty, we see the mention about the envoy of Fu-lin Kuo, ordinarily identified with the Byzantine Empire, who came to Chang-an and presented "Ti-Yeh-Ch'ieh" to the then Emperor of China. The late Prof. F. Hirth thought-that the Ti-Yeh-Ch'ieh should be the theriaka (theriac, treacle) which is a very famous antidotal drug invented by a certain Greek physician in the 2nd century. We can find in various Chinese documents prior to the date of the above mentioned envoy of Fu-lin country the name of this medicament. For example, in "Shin-hsiu-pentsao" (New Materia Medica), compiled in 659 A. D., we read that this thing was a drug of the far western countries and foreign people brought it to China from time to time. In Japan, the oldest existent book which contains the record concerning the theriaka is "I-hsin-fang" written in 980 A. D. by Tamba-no-Yasuyori. On the other hand, it is not difficult to find out many articles relating to "tiryaq", theriaka, from among the Islamic literary works. Through these materials, we should be able to make clear in detail the prescription of this antidote and to know how it was and is still popular in the Middle East society. In Japan, the theriaka was introduced again since the 16th century by the Europeans. The writer thinks that the historical study of the diffusion of this kind of medicine is not only interesting from the standpoint of folklore, but it will be able to contribute to clarify the currents of cultures between the East and the west.