The 2001 Quadrennial Defense Review called for the Navy to provide more warfighting assets more quickly to multiple locations. Subsequently, the Navy made a preliminary decision to homeport a nuclear-powered aircraft carrier at Naval Station Mayport, Florida, which was affirmed by the 2010 Quadrennial Defense Review. In House Report 111-491, accompanying a proposed bill for the Fiscal Year 2011 National Defense Authorization Act (H.R. 5136), GAO was directed to develop an independent estimate of the total federal costs for the proposed homeporting. GAO's objectives were to (1) develop an independent estimate of the full life-cycle costs to homeport a nuclear aircraft carrier at Mayport and (2) determine to what extent the Navy's estimate meets the characteristics of a high-quality cost estimate. To do this, GAO worked with a firm experienced in preparing life-cycle cost estimates for major federal acquisitions and compared the Navy's cost estimating practices with the best practices in GAO's Cost Estimating and Assessment Guide. GAO recommends DOD take several actions to improve the quality of its Mayport cost estimate.