This report and its appendixes provide background information on Hamas, or the Islamic Resistance Movement, and U.S. policy towards it. It also includes information and analysis on (1) the threats Hamas currently poses to U.S. interests, (2) how Hamas compares with other Middle East terrorist groups, (3) Hamas's ideology and policies (both generally and on discrete issues), (4) its leadership and organization, and (5) its sources of assistance. Finally, the report raises and discusses various legislative and oversight options related to foreign aid strategies, financial sanctions, and regional and international political approaches. In evaluating these options, Congress can assess how Hamas has emerged and adapted over time, and also scrutinize the track record of U.S., Israeli, and international policy to counter Hamas. Hamas is a Palestinian Islamist military and sociopolitical movement that grew out of the Muslim Brotherhood. The United States, Israel, the European Union, and Canada consider Hamas a terrorist organization because of (1) its violent resistance to what it deems Israeli occupation of historic Palestine (constituting present-day Israel, West Bank, and Gaza Strip), and (2) its rejection of the off-and-on peace process involving Israel and the Palestine Liberation Organization (PLO) since the early 1990s. Since Hamas's inception in 1987, it has maintained its primary base of political support and its military command in the Gaza Strip-a territory it has controlled since June 2007-while also having a significant presence in the West Bank. The movement's political leadership is currently headquartered in exile in Damascus, Syria. Hamas receives assistance and training from Iran, Syria, and the Lebanese Shiite militant group Hezbollah. Hamas is often discussed alongside other groups in the region that engage in militant and terrorist activities to achieve their ends, yet Hamas has confined its militancy to Israel and the Palestinian territories-distinguishing it from the broader aspirations expressed by Al Qaeda and its affiliates. The overarching U.S. goal regarding Hamas is to deter, transform, marginalize, or neutralize it so that it no longer presents a threat to Israel's security, to a peaceful and lasting resolution of the Israeli-Palestinian conflict, or to other U.S. interests-either in its own right or as a proxy of Iran or other actors. Various legislative and policy initiatives designed to accomplish this goal have at most achieved temporary or partial success. It is possible to conclude that U.S. and other international support for Israel and the Palestinian Authority/PLO dominated by Fatah (Hamas's main rival faction) has been counterproductive to some extent when comparing Hamas's domestic, regional, and international strength in the early 1990s-measured by factors such as popularity, military force, and leverage with other actors (including Israel and Fatah)-to its current strength. The Israeli-Egyptian closure regime in Gaza and various U.S. and international initiatives constrain and isolate Hamas to a point and may exacerbate its internal organizational tensions and tactical disagreements. Yet, the threats Hamas continues to pose to Israel, to prospects for a two-state solution and to the future of Palestinian democracy present considerable risks and difficult trade-offs for any U.S. policy decisions going forward.