This is the first book-length exploration in English of issues of medicine and society in premodern Japan. The book expands the parameters of the study of medicine in East Asia and introduces the dynamics of interaction and exchange that coursed through the East Asian macro-culture. It explores these themes primarily through the two extant works of the Buddhist priest and clinical physician Kajiwara Shōzen (1265–1337), who was active at the medical facility housed at Gokurakuji temple in Kamakura, the capital of Japan's first warrior government. Shōzen was a beneficiary of the efflorescence of trade and exchange across the East China Sea that typifies this era. His break with the restrictions of Japanese medicine is revealed in Ton'ishō (Book of the Simple Physician) and Man'apō (Myriad Relief Formulas). Both of these texts are landmarks. This book brings to the fore the range of factors that influenced the Japanese acquisition of Chinese medical information. It offers the first substantive portrait of the impact of the Song printing revolution in medieval Japan and provides a rare glimpse of Chinese medicine as it was understood outside of China. It is further distinguished by its attention to materia medica and medicinal formulas and to the challenges of technical translation and technological transfer in the reception and incorporation of a new pharmaceutical regime.