This Chatpter is a dialogue from the Yellow Emperor’s Classic of Internal Medicine, exploring the nature and treatment of bi, a condition encompassing various obstructive disorders. Bi is explained as arising from imbalances of wind, cold, and dampness, affecting different parts of the body depending on the season and the predominant pathogenic factor. The discussion details the symptoms and organ involvement of bi, its progression, and the role of acupuncture in its treatment. Finally, it examines the relationship between bi and the body's energy systems, the nutritive and defensive qi.