The rise of the modern private military industry in the 1990s is explained and claims about the benefits and hazards of privatized military force are evaluated from a public interest perspective. Evidence about the cost effectiveness of employing private military companies (PMCs) is found to be inconclusive, although outsourcing has the potential to increase military flexibility and provide states with newly emerging capabilities in the short run. Governments are shown to have "hidden" motives for outsourcing military functions. It is argued that most benefits of privatization are conditional and that PMC-related hazards threaten to do long-term damage to the rule of law (both nationally and internationally), to the militaries which most rely on private contractors and to the fabric of constitutional democracy.