This paper describes the development of an automated authority control system for the Genealogical Society of Utah, which has large holdings of microfilmed records from many nations, including civil registration, parish registers, local records, and census records. The key function of the library is the identification of people. From the beginning, the task of the library's bibliographic control system has been to efficiently and correctly identify and make accessible the library's holdings. The catalog, now quite old, contains several eras of cataloging and includes subject cataloging, first introduced in the 1960s. Gradually modern cataloging techniques including authority files have been introduced into the control system. In the 1970s, a decision was made to go online with an interactive computer catalog system. Details of the computer's authority control operation and the authority control scheme are presented with numerous illustrations. Special features of the process include a name extraction program and a locality extraction program to allow users simplified entry into the genealogical files. (RAA)