SCORPIO (Subject Content-Oriented Retriever for Processing Information On-line), a set of computer programs developed by the Library of Congress for use by the Library Library's staff, is described. Intended as a users guide for those not trained in data processing, this document presents the system's general characteristics together with a listing of its commands. Examples of their use in searching the system files are provided. The appendixes include: (1) a listing of special display commands available to the user, (2) a description of the contents and organization of the files that can be searched--Legislative Information File, Bibliographic Citation File, Major Issues File, and the National Referral Center File, (3) operating instructions for commonly used remote terminals, and (4) a listing of SCORPIO messages that the user may encounter. (DGC)