Although there are no cases from which researchers can draw lessons about how the U.S. population will react to an unprecedented act of bioterrorism, experience with natural and technological disasters and disease outbreaks reveals a pattern of generally effective and adaptive collective action. Failure to involve the public as a key partner in the medical and public-health response could hamper effective management of an epidemic and increase the likelihood of social disruption. This paper presents and discusses five guidelines for improving planning for and the response to the release of a biological weapon by increasing the involvement of the public. First, planners should appreciate that panic is rare and preventable. Planners should carve out a constructive role for the general public in planning and responding to a bioterrorism event. There should be a release of timely, accurate public information, including instructions in personal protective measures. Second, enlist the general public as a capable partner. Civic organizations can be used to assist with information dissemination, outbreak monitoring, and medication distribution. Third, think beyond the hospital for mass-casualty care. There should be plans for home-based patient care and infection control as part of plans for a communitywide response to deal with mass casualties. Lay and alternative care providers should be involved; and family, neighbors, and community groups can be useful in identifying patients, disseminating information and therapies, and in assisting affected individuals in obtaining treatment. Fourth, provide information, which is as important as providing medicine. A health communication strategy should empower the general public, and it should be multilingual and culturally relevant. Information on the limits of what is known should be timely and forthcoming. Fifth, assume that the public will not take the pill if it does not trust the doctor. The public must be educated prior to an attack regarding what is being done to prepare and develop a response strategy. There should be an open flow of information during an attack through mass media outlets and interpersonal exchanges. Participatory decision making processes should include the public, particularly in regard to how to allocate scarce resources and institute epidemic controls that compromise civil liberties. 51 references