High-performance computing refers to the use of advanced computing technologies to solve highly complex problems in the shortest possible time. The federal High Performance Computing and Communications Initiative of the Advanced Research Project Agency (ARPA) attempts to accelerate availability and use of high performance computers and networks. The House Armed Services Committee asked the General Accounting Office (GAO) to assess this program, particularly the agency's distribution of advanced computers to research sites, its interaction with the research community, and the balance between hardware and software. Interviews with agency and industry representatives and a review of documents were conducted. Results indicate that the ARPA has fostered significant advances, but with several shortcomings. Placing of new computers has focused on just a few machines. Limited interactions with the technical community may be hindering progress toward ambitious program goals. Much progress has been made in hardware development, but software remains too primitive to make massively parallel processing systems useful. Recommendations for improvement are presented. Four appendixes provide details about methodology, placement of machines, and project selection, and list contributors to the report. Five tables contain study findings, and two figures illustrate computer applications and product selection. (SLD)