Pursuant to a congressional request, GAO reviewed the federal government's management of its motor vehicle fleet, focusing on: (1) obstacles to achieving cost-efficient fleet management; and (2) public and private fleet management practices that might be applicable to the federal fleet. GAO found that: (1) obstacles to cost-efficient federal fleet management include the lack of uniform guidance for conducting valid cost-comparison studies, insufficient vehicle information, unpredictable funding, and restrictive agency solicitations that limit private-sector competition; (2) in 1993, the Office of Management and Budget (OMB) issued uniform guidance for conducting valid cost-comparison studies in response to a task force recommendation; (3) most federal agencies continue to operate their fleets without complying with statutory requirements for cost-efficiency; (4) improving fleet management requires a cost-conscious culture; and (5) essential management practices for cost-effective fleet operation include assessing vehicle utilization to determine the appropriate size of the fleet, establishing a fleet operation baseline, having needed information and supporting management information systems to assess performance, comparing costs and performance with the best fleets, funding the fleet through a revolving fund, and centralizing fleet management responsibilities.