This Congressional Budget Office (CBO) paper (Pub. No. 3053), which was prepared at the request of the Senate Committee on the Budget, examines the use of contractors in the Iraq theater from 2003 through 2007. It provides an overview of the federal government's costs of employing contractors in Iraq and in nearby countries, the type of products and services they provide, the number of personnel working on those contracts, comparisons of past and present use of contractors during U.S. military operations, and the use of contractors to provide security. CBO also investigated the command-and-control structure between the U.S. government and contract employees and the legal issues surrounding contractor personnel working in Iraq. This paper was prepared by Daniel Frisk and R. Derek Trunkey of CBO's National Security Division under the supervision of J. Michael Gilmore and Matthew Goldberg.