For over a thousand years, the works of Zhang Zhongjing ()–the Shanghan lun () and the Jingui yaolue ()–have been the both the foundation and the highest level of study and practice for Chinese herbalists. Prior to modern times, almost all serious clinicians memorized both texts, and even today, many clinicians in China continue this tradition. Why? What has made these two thousand year-old texts so useful and important? In this talk, Stephen Boyanton discusses the answers to this question and shows why it is impossible to practice advanced Chinese herbal medicine without a solid grasp of these two texts.