Failure to implement effective risk communication can undermine preparedness efforts, exacerbate disasters, and impede the recovery process. When conducted appropriately, risk communication can significantly increase community resilience, mitigate the cost of disasters, and save lives. The Understanding Risk Communication Best Practices and Understanding Risk Communication Theory documents are designed to provide emergency managers with the foundations for conducting effective risk communication during the preparedness, response, and recovery phases of all homeland security related hazards. Effective risk communication requires a strong understanding of complex factors including trust between the communicator(s) and the audience(s), cognitive involvement and uncertainty of the audience, cost-reward tradeoffs, emotional responses to risk, and understanding and acknowledging diverse audiences. Risk communication is especially challenging now as new media changes the landscape for both communicators and their audiences.