Warning messages transmitted to populations at risk from an accidental release of chemical agent must be carefully designed to maximize appropriate responses from affected publics. This guide develops an approach for preparing Emergency Broadcast System (EBS) messages for the Chemical Stockpile Emergency Preparedness Program (CSEPP). Sample messages illustrate the application of this approach. While the sample messages do not cover every emergency situation, the texts are generic in that accident and location specific factors can be incorporated into the final message developed by local emergency planners. Thus they provide a starting point, not an end product, for emergency planners.