The UN employs about 85,000 military and civilian personnel in peacekeeping operations in 16 countries. The United States has provided about $1 billion annually to support UN peacekeeping operations. In addition, the United States has led and participated in many such operations. UN reports and congressional hearings have raised concerns about accountability for UN peacekeeping operations and the need for reforms. We were asked to provide information relating to the cost and relative strengths of UN and U.S. peacekeeping. In particular, we have (1) compared the cost of the ongoing UN Stabilization Mission in Haiti with the cost that the United States would have incurred had an operation been deemed in the U.S. national interest and undertaken without UN involvement; (2) analyzed factors that could materially affect the estimated costs of a U.S. operation; and (3) identified the strengths of the United States and the UN for leading the operation. We developed our cost estimate of a U.S.-led operation using cost models from the Departments of Defense and State. The estimate is based on various military assumptions, such as the use of primarily active duty troops. It includes only those costs directly attributable to the operation that would not otherwise be incurred.