The Global Nuclear Detection Architecture (GNDA) is a multi-layered system of detection technol., programs, and guidelines designed to enhance the nation¿s ability to detect and prevent a radiological or nuclear attack. Among its components are existing programs in nuclear detection operated by other fed. agencies and new programs put into place by the Domestic Nuclear Detection Office (DNDO). Contents of this report: (1) Intro.: Fed. Efforts; DNDO; (2) What is the GNDA?: Layered Defense; Methodology and Metrics for Eval¿n.; Priority Setting; Interagency Coord¿n.; (3) Priorities and Funding Levels Within the GNDA; Balance Between Incremental and Transformational Changes to the GNDA; Long-Term Maint. of the GNDA; R&D Coord. Tables.