The ninth edition of the Thesaurus of Psychological Index Terms provides the psychological vocabulary used to search the 1.7 million records in the PsycINFO database. The Thesaurus contains well over 5,000 index terms with easy-to-read scope notes and definitions. This easy-to-use reference tool is divided into three sections: the Relationship Section, the Rotated Alphabetical Terms Section, and the Clusters section. In the Relationship Section, each term is listed alphabetically and is cross-referenced and displayed with its hierarchical structure denoting broader, narrower, and related terms. The Rotated Alphabetical Section list terms in alphabetical order by each component word. Finally, the Clusters Section provides groups of terms that are conceptually related and displayed under broad subject categories. This essential reference tool is completely integrated with essential tips on searching along with a quick reference guide to all online and CD-ROM systems.