Communication is a critical component of helping individuals prepare for, respond to, and recover from emergencies. However, there is limited knowledge about how to best communicate with at-risk populations in emergencies. To inform this gap, RAND researchers, under contract by the U.S. Department of Health and Human Services Office of the Assistant Secretary for Planning and Evaluation (ASPE) (Task Order 07EASPE000074), sought to understand the communication needs and to identify strategies with potential for improving risk communication with at-risk populations. This one-year study presents the results of an assessment that involved review of the literature on emergency preparedness risk communication and public health messaging strategies; the compilation of educational and outreach materials for emergency preparedness communication with at-risk populations; and site visits in three states and the Washington, DC area to identify gaps in the practice of risk communication with at risk populations. The findings should be of interest to state and local emergency managers, community based organizations, public health researchers, and policy makers.