The first edition of USAMRIID's Medical Management of Biological Casualties Handbook was released in 1993. Known informally as the "Blue Book," it has been revised regularly over the past 27 years. More than 213,000 hard copies have been distributed to military and civilian healthcare providers around the world. The Blue Book is in the public domain and is available for free download. This important work serves as the primary reference document for USAMRIID's resident and off-site Medical Management of Biological Casualties (MMBC) course. This 9th edition has been revised and updated to better present our current understanding of the optimal medical management of diseases and syndromes caused by biological threat agents. The Table of Contents remains unchanged from the previous edition. This resource is available in a .pdf format and may be downloaded from the Reference Material section of USAMRIID's website, https: //www.usamriid.army.mil. For more detailed information the reader is referred to larger Textbook of Military Medicine (TMM) - Medical Aspects of Biological Warfare, which is also available for download from the above website. Our goal has been to make this reference useful for the healthcare provider on the front lines, whether on the battlefield or in a fixed clinic, where basic summary and treatment information is quickly required. We are constantly striving to make it a better product and would like your feedback to make future editions more useful and readable. Thank you for your interest in this important subject.