Summary: Pursuant to a congressional request, GAO reviewed the Department of the Navy's Tactical Advanced Computer-4 (TAC-4) procurement which allows other Department of Defense and civilian agencies to purchase equipment without full competition and oversight. GAO found that the Navy: (1) has not completed its systems requirements planning and analyses and has not studied the feasibility and costs of procurement alternatives; (2) does not have a plan to integrate its tactical and non-tactical systems under the procurement; (3) has overestimated the maximum number of systems that will be ordered from the TAC-4 contract; (4) requirement that the systems provide binary compatibility rather than software portability is restrictive and will limit competition; (5) will have difficulty managing the TAC-4 contract, since it will be a large schedule contract for numerous users with diverse system requirements; (6) does not plan to validate other agencies' requirements analyses and justifications; and (7) plans to give contract administration responsibility to one of its research facilities that has no experience in processing orders for users outside of the Navy.