The threat of terrorism involving radioactive materials has grown significantly in recent years. A large-scale incident involving radiationâ€”whether through an improvised nuclear device (IND), a radiological dispersal device (RDD), or a radiological exposure device (RED)â€”could pose a host of preparedness and response challenges. Among the most important of these is effective communication. Providing clear, comprehensible, credible information to people in a timely fashion is vital for reducing deaths, injuries and illnesses, reducing psychological impacts, and mitigating terror effects of the incident. ; Federal agencies have a variety of roles and responsibilities related to communicating with the public before, during, and after an event. To better understand the various efforts currently under way, the Centers for Disease Control and Preventionâ€™s (CDCâ€™s) Radiation Studies Branch (RSB) contracted with Macro International Inc. to convene a roundtable of representatives from Federal agencies with responsibility for communicating with the public about radiation emergencies. The objectives of this meeting were to: provide a forum where participants could discuss with one another their respective roles and responsibilities in communicating to the public in the event of a radiation emergency; identify existing radiological/nuclear emergency messages and materials for the general public; learn what communication planning activities are underway or planned across the various agencies, and discuss how the lines of communication can be broadened across agencies. ; The roundtable took place January 28â€“29, 2009, at CDCâ€™s Global Communications Center in Atlanta, GA. (See Appendix A for the roundtable agenda.) The program began with remarks by Dr. Michael McGeehin (Director, Division of Environmental Hazards and Health Effects [EHHE], National Center for Environmental Health, CDC) and Dr. Charles Miller (Chief, Radiation Studies Branch in EHHE, CDC) set the stage for the roundtable by emphasizing the role of communication in our ability to respond to a radiation emergency and by stressing the importance of interagency coordination. Next, participants described their roles and their agenciesâ€™ organizational structures with respect to communicating in the event of a radiation emergency. Then participants had the opportunity to share their agenciesâ€™ existing communication messages and materials as part of small group and large group discussions. Roundtable participants then discussed the gaps and challenges related to the existing messages and materials. ; The second day of the meeting the roundtable focused on the practical application of existing public communication efforts across the participating agencies. Thearis Osuji (Macro) presented some of the results of the recent cognitive testing of messages conducted by Macro on behalf of RSB. Dr. Steven M. Becker (University of Alabama at Birmingham) presented two different radiation emergency scenarios to help participants apply discussions about communication to possible real-world emergencies. At the conclusion of the roundtable, participants agreed that continued interagency coordination and dialogue about communication before, during, and after an event are necessary. ; The roundtable provided a forum that allowed communicators across a number of Federal agencies to share information, strategies, and challenges in developing and providing communication messages and materials to the public in preparation for, and in response to, a radiation emergency. Throughout the discussion, several â€œbig pictureâ€? questions were brought up that may be addressed in future interagency efforts: Should radiation pre-event education be a priority in light of limited resources? Would this be effective or would pre-event education about radiation either be ignored or scare the public?; What types of pre-event education are possible?; How might these mesh with other preparedness efforts/campaigns? How can radiation-related technical terms and concepts be simplified into terms that lay people can understand?; Can we achieve cross-agency agreement on messages, and if so, how? How can we come to consensus across agencies and disciplines with our different responsibilities, emphases, and interests?; Can we get radiation emergency subject matter experts to agree on a unified set of messages?; What communication strategies are more effective: direct to the public or through intermediaries?; What can and cannot be addressed using an all-hazards approach to preparedness and response? ; Overview -- Participant introductions, roles, and responsibilities -- Existing communication messages and materials -- Presentation of RSBâ€™s cognitive testing results -- Practical application scenarios and discussion -- Concluding statements and recommendations -- Appendix A. Agenda -- Appendix B. Descriptions of federal agency organizational structures -- Appendix C. Summary of existing government and nongovernment public-facing radiological communications materials -- Appendix D. Glossary of frequently used terms.