Summary: Pursuant to a congressional request, GAO provided information on the potential costs, to NATO and its future members, of expanding the North Atlantic Treaty Organization's (NATO) membership. GAO noted that: (1) most of the costs of NATO expansion will be borne by the aspiring member states; (2) NATO, through the Partnership for Peace Program, has already begun to reach out to Central and Eastern Europe nations by providing them with additional security and helping potential member states become familiar with NATO operations; (3) although NATO will likely have to spend common funds in new member nations, funding would be limited to building infrastructure that is required to meet NATO interoperability standards; (4) funding for new individual members would probably not exceed $50 million during the first 3 to 5 years of their NATO membership; (5) the total costs of NATO expansion cannot yet be determined because NATO has not defined country-specific military requirements for new member countries; (6) new NATO members may receive bilateral assistance to aid them in making the adjustments necessary for their membership; and (7) the United States expects to spend an additional $12.5 million in 1996 to help potential new member countries meet NATO requirements.