We estimate that it would cost the United States about twice as much as it would the UN to conduct a peacekeeping operation similar to the UN mission in Haiti. The UN budgeted $428 million for the first 14 months of the mission, of which the United States was responsible for $116 million. A similar U.S. operation would have cost an estimated $876 million. Virtually the entire cost difference can be attributed to three major elements: civilian police, military pay and support, and facilities. First, the estimated cost of deploying U.S. civilian police is $217 million or about 8 times the $25 million budgeted by the UN for international police officers. Compensation rates for U.S. police include higher costs for salaries, special pay and training, whereas the UN pays police a standard daily allowance. Second, we estimated that U.S. military pay and support would cost $260 million, compared with $131 million in the UN budget, and reflects higher salaries and higher standards for equipment, ammunition, and rations. Third, U.S. facilities-related costs would be twice those of the UN, reflecting the cost of posting U.S. civilian personnel in a secure embassy compound. Several factors could affect the estimated costs of a U.S. operation, including the mix of reserve and active duty troops and the rate of troop deployment. When we varied these factors for example, by increasing the number of reserve troops deployed the estimated cost for a U.S. operation increased.