In recognition that no single country possesses all the answers to the critical scientific, institutional and legal questions associated with combating nuclear and radiological terrorism, the 2005 Workshop and these proceedings were structured to promote wide-ranging, multi-national exploration of critical technology needs and underlying scientific challenges to reducing the threat of nuclear/radiological terrorism; to illustrate through country-specific presentations how resulting technologies were used in national programs; and to outline the role of legal, policy and institutional frameworks in countering nuclear/radiological terrorism. One key outcome of this book is a better understanding of the independent contributions from across the international community of the scientific and technological components and the legal, policy and institutional components to combating nuclear/radiological terrorism. The book can serve as a tool for communicating the outcomes of the workshop to the multi-national scientific communities engaged in combating nuclear/radiological terrorism, and to those working at governmental and policy levels.