The Marine Officer’s Guide, 7th Edition describes in detail the Marine Corps as a military institution of the United States and, in so doing, delineates the characteristics of the men and women who constitute the Corps. The Guide supplements, but does not supplant, official regulations and instructions. It can help an officer to acquire quickly a stockpile of information, but it does not relieve the officer of his or her obligation to know the published regulations that govern our Corps. I have endeavored to provide sound advice and up-to-date information on professional matters of note to the Marine officer. I have described customs and usages that are current and not at variance with “the book.” I have also deleted some practices that have become anachronistic, and persons in search of nostalgic material can refer to preceding editions for them. Many a well-worn copy sits ready at hand on the bookshelves of the officer corps, and officers of all grades have grown accustomed to its reliability and utility. This seventh edition reflects all the changes in the organization of the Corps fostered by the evolving military establishment of the United States. A modern corps, shaped in so many ways by the Great Pacific War of 1941-1945, now reflects the Gulf Conflicts and the passing of the era of superpower rivalry and the century of the world wars. What remain remarkably unchanged, however, are the character of the Marine Corps and the keen pursuit of excellence in the profession of arms that its officer corps reflects.