What has it meant to be labeled the "second-front" in the "global war on terror"? Have Southeast Asian states accepted that the primary threat their countries face is Al-Qaeda-inspired terrorist violence, or are other security concerns deemed more pressing? This study investigates threat perceptions in four Southeast Asian countries: Indonesia, Malaysia, the Philippines, and Singapore. It probes the extent to which their security concerns align with those of Washington, together with their preferred means for dealing with the phenomenon of terrorist violence. The central findings are that, in all four countries, the U.S. counterterrorist security agenda has shaped security perceptions as well as security behavior, though to a greater extent in the Philippines and Singapore than in Indonesia and Malaysia. However, the most important effect in Southeast Asia of this change in the U.S. security priority after 9/11 has been sociopolitical in nature, even where an individual government might not perceive the threat from terrorism to be the major security challenge that it faces. In each of the four states, involvement in the U.S. decision to give overwhelming attention to counterterrorist action has sharpened the focus on long-standing security concerns, especially those connected with the security of the political regime or unity of society. In sum, these countries' domestic concerns interact in complex and subtle ways with their security relationship with the United States, as well as affecting the methods that the individual governments have used to deal with actual or potential terrorist violence inside their countries.