[en] This User's Manual is intended to contain all the information necessary for a prospective user of the Part 21/50.55(e) Data Base (called the 21/55 DB, for short) to sit at a suitable computer terminal and obtain information from the data base, as well as inputting certain types of information designed for input by NRC personnel from remote terminals. The 21/55 DB contains coded information from the reports submitted to NRC by reactor construction licensees and certain suppliers of equipment and components to nuclear facilities licensed to operate, under the requirements of 10 CFR 21 and 10 CFR 50.55(e). The first section presents the general structure and philosophy of the data base. Then the Manual gives step-by-step instructions for logging on, manipulating and selecting data, obtaining desired output, and inputting the information which is designed for insertion from the remote NRC terminals. Last there is a description of the information in the base, its nature, and the codes used