In 1995, the National Science Foundation (NSF) created a special account to fund large (several tens of millions of dollars) research facilities. Over the years, these facilities have come to represent an increasingly prominent part of the nationa (TM)s R&D portfolio. Recently concern has intensified about the way NSF is selecting projects for this account. In 2003, six U.S. Senators including the chair and ranking member of the Senate Subcommittee on VA, HUD, and Independent Agencies Appropriations expressed these concerns in a letter to the NRC asking it to a /review the current prioritization process and report to us on how it can be improved.a This report presents a series of recommendations on how NSF can improve its priority setting process for large research facilities. While noting that NSF has improved this process, the report states that further strengthening is needed if NSF is to meet future demands for such projects.