The United States Postal Service (USPS) operates the largest and most visible civilian vehicle fleet in the world. To accomplish its mission, the Postal Service must have dependable sources of fuel for its 208,000 vehicles. A fleet operation of that size must also constantly seek ways to reduce operating costs, and United States energy policy emphasizes the goal of reducing reliance on petroleum fuels in the highway sector. In furtherance of these goals and that of environmental protection, the USPS also operates the nation's largest fleet of alternative fuel vehicles. The USPS is committed to the continuing expansion of its alternative fuel vehicle (AFV) fleet and has assumed a strong leadership role in the development and deployment of alternative fuel vehicle technologies. This paper provides an overview of the Postal Service's current AFV program and its history.