The FBI's NCIC system is described in terms of the types of files maintained, the nationwide telecommunications access to them, and the procedures for using the system and maintaining data quality. Another section describes the parallel files maintained by the States and municipalities and the way in which these State and local systems operate in conjunction with the FBI's national system. Federal and State laws dealing with the establishment and operation of hot file systems are also described. An analysis of court decisions dealing with hot file information covers the duty of criminal justice officials to maintain complete and accurate records, the risk of liability for wrongful maintenance or use of hot file information, and the question of the legality of arrests based on invalid or inaccurate hot file information. The NCIC system includes data quality procedures that can prevent the reliance on inaccurate information, but some State and local agencies do not follow these procedures carefully. High national standards, continuing audits, and appropriate training are all essential. Additional recommendations; details of the California, Florida, and Dade County (Fla.) systems; footnotes; and figures.