The second Nuclear Security Summit on 26–27 March 2012 in Seoul provides an important opportunity to gauge international consensus on the threat posed by nuclear terrorism, and to evaluate progress in the development of multilateral cooperative efforts to prevent it. However, the ‘nuclear security’ agenda has long been complicated by the complexity of the issues it covers and diverging perceptions of the risks and threats in this area. Further complications involve the politics that have constrained the development of formal cooperative approaches and the patchwork nature of the existing multilateral policy architecture. While the Summit is unlikely to go very far in mitigating these complications, it will nonetheless provide impetus to multilateral efforts to strengthen the international regulative framework in this area and, in the process, to develop the norm of nuclear security. Beyond Seoul several priorities stand out. Nuclear safety and nuclear security need to be approached in a more balanced way by the International Atomic Energy Agency, and it must also be allowed to adopt a more joined-up, and less stove-piped, approach to nuclear governance across the safeguards, safety and security fields. Developing countries that are concerned by growing demands for strengthened nuclear security arrangements need greater reassurance from those proposing them that these will not undermine their rights under the Nuclear Non-Proliferation Treaty to pursue civil applications of nuclear energy. Greater progress also needs to be made in universalizing the key nuclear security conventions and their amendments, and attention should be given to how momentum and high-level political buy-in to the nuclear security agenda can be maintained in the future both as part of, and beyond, the Nuclear Security Summit process.