For 32 years at the Library of Congress I have had the privilege of helping bring readers and books together through subject cataloging. My work involves analyzing social science materials, describing their contents with controlled vocabulary terms (Library of Congress Subject Headings, or LCSH), and determining their shelf location in scores of libraries all over the world by the assignment of a Library of Congress Classification number. A behind-the-scenes look at subject cataloging should help readers understand better how libraries and bookstores determine where to place books on their shelves, and help authors guide the placement of their books into specialties and onto those shelves. Library of Congress (LC) subject cataloging data clearly determine the retrievability and the shelf location of books in libraries, but that's only part of the story. Over 90 percent of mainstream U.S. publishers participate in LC's Cataloging in Publication Program (CIP), in which the cataloging is done before publication, so that the cataloging record is published in the book. Book jobbers, such as Baker & Taylor and Blackwell's, make use of LC's pre-publication subject cataloging data from the CIP program to notify libraries about upcoming books that match their collections profile. R. R. Bowker also furnishes LC subject cataloging data in many of its publications. Two Bowker titles, widely used in both libraries and bookstores, are Subject Guide to Books in Print and Forthcoming Books. A growing number of web sites use LC subject headings to categorize their data, and some bookstores consult the LC subject cataloging data printed on the back of the title page of most U.S. publications to help decide where to shelve the book. The Trover Shop, a Capitol Hill bookstore and a neighbor of the Library of Congress, frequently does this. What are the subject cataloging guidelines at the Library of Congress? The subject cataloger examines the book to determine the focus of its subject and selects one or more headings from LCSH that best summarize the work and provide access to its most important topics. A heading is assigned for a topic only if at least 20 percent of the work is about that topic. However, headings for individuals, families, corporate bodies, projects, events, buildings, or named products that are significant to the contents of the work are assigned even if discussion of them does not constitute 20 percent. The number of headings varies. One is enough for an introductory sociology textbook. The upper limit is ten. The subject cataloger assigns headings that are as specific as the topics they cover. A work dealing with the Animal Rights Movement, the Gay Liberation Movement, the Men's Movement, and the Antinuclear Movement would receive a subject heading for each. Next, up to four subtopic headings may be assigned to a work. If the work also discusses the theory of social in general, the heading Social movements would also be assigned. Since most American publications are currently being cataloged at the Library of Congress as CIPs, the subject cataloger often has only introductory pages and a table of contents upon which to base his or her decision. Authors who provide a synopsis of their book greatly increase the likelihood that it will be cataloged accurately and find a place on the shelf adjacent to similar works. Authors who consider their books to be significant contributions to a general topic (e.g., social movements) should make that clear in their synopses to ensure that a subject heading for the general topic will be added. Subject headings are often subdivided, as appropriate, by topic (e.g., SocializationCross-cultural studies), place, time period, or form (e.g., Sociology Dictionaries). The first subject heading usually corresponds tO the LC classification number. While subject headings are designed to provide access to books on similar topics or in a given field, the LC classification number groups together books on the same topic. This allows patrons of libraries with open stacks to browse freely among them and, if they know the classification scheme employed, turn readily to the shelves containing books on the subjects that interest them. The classification number for each book is selected from published schedules which are also available to the library community. This classification number normally corresponds to the first subject heading assigned. Traditional LC classification practices dictate that some works, considered by many scholars to be sociology, will be classed by LC outside of the normal sociology range (i.e.,