This book is meant to assist library professionals who are automating their catalog or who are switching from "Sears List of Subject Headings" to the Library of Congress Subject Headings (LCSH) as subject authority. A first-check source for the most frequently used headings needed in media centers and public libraries, this third edition has several thousand new and revised entries to assist in applying LCSH and Annotated Card Program (AC) headings. A comprehensive subject authority and companion to the LC list of headings, this compilation has been supplemented with hundreds of names from the LC authority file, and it incorporates current modifications of LCSH (23rd edition) for subject access to general and children's material. Of the approximately 30,000 headings listed, thousands include cross-references. Also new to this edition, MARC (MAchine-Readable Cataloging) codes are provided for ambiguous headings to simplify entering them in computerized catalogs. The introduction provides information on: the Library of Congress's Annotated Card Program; format of the subject heading list; using the subject heading list; using free-floating phrase headings; using free-floating subdivisions; types of subdivisions; pattern headings; categories with no pattern headings; table of pattern headings; caveats; and format of the free-floating subdivision list. There is also a key to free-floating subdivisions and a list of free-floating subdivisions. (AEF)