Book excerpt: This is a translation and annotation of Li Dong-yuan's Pi Wei Lun; by Bob Flaws. With so much new research in China on the ideas and formulas of Li Dong-yuan, we feel this book is one of the most important pre-modern texts in Chinese medicine for 21st century clinicians. Bob has undertaken the task of a fresh translation of this book, this time including detailed commentary, relevant case histories and random clinical trail reports for each chapter.