GAO reviewed pertinent legislation and Department of Defense regulations; interviewed officials; reviewed billing and collection procedures; and reviewed the audit objectives, scope of work, and work performed by the Defense auditors in Iran. The review found that although the Defense Security Assistance Agency was responsible for ensuring that all costs incurred in providing technical assistance and training in Iran were recovered, they had not taken action to recover the roughly $28.5 million in costs incurred but not included in sales contracts with Iran. Defense had also done nothing to recover about $20.7 million in other costs to support the technical assistance and training program in Iran, such as transporting to Iran personnel-support items. Defense should promptly implement the recommendations of Defense auditors to identify all costs associated with providing technical assistance and training to the Iranian Government and, consistent with the provision of the Foreign Military Sales Act and the Department of Defense Form 1513, seek reimbursement for such costs. Any costs that are not recovered should and can be subsequently billed. The longer the delay in billing Iran for unrecovered costs, the more difficult it will be to recover these costs. The agency should also include in future foreign military sales contracts any additional estimated costs associated with providing technical assistance and training services in Iran. Procedures and criteria used for identifying costs that should be reimbursed by Iran should be reevaluated, to ensure that all costs the U.S. Governments incurred in providing technical assistance and training in Iran are recovered.