In 1995, the United States banned exports to Iran of most U.S. goods without a Treasury Department license. In 2008, the U.S. media, citing U.S. government statistics, reported that U.S. firms were exporting numerous goods to Iran. The statistics are maintained by the Census Bureau and are based on data filed by exporters or their agents. The United States has also generally banned unlicensed transshipments of U.S. goods to Iran via other nations. In this report, GAO assesses the extent to which (1) U.S. trade statistics accurately depict exports to Iran, (2) Treasury licenses exports to Iran in accordance with the trade restrictions and provides licensing data to enforcement agencies and Congress, and (3) Iran obtains U.S. military and dual-use goods through transshipment. GAO analyzed Census export data, a randomly selected sample of Treasury export licenses, Treasury licensing information systems, and U.S. government transshipment data. It also interviewed relevant U.S. government officials.