The United States has not suffered significant psychosocial or medical consequences from the use of biological weapons within its territories. This has contributed to a "natural" state of denial at the community level. This denial could amplify the sense of crisis, anxiety, fear, chaos, and disorder that would accompany such a bioterrorist event. A key part of primary prevention involves counteracting this possibility before an incident occurs. Doing so will require realistic information regarding the bioterrorism threat followed by the development of a planned response and regular practice of that response. Unlike in natural disasters or other situations resulting in mass casualties, emergency department physicians or nurses and primary care physicians (working in concert with epidemiologic agencies), rather than police, firemen, or ambulance personnel, will be most likely to first identify the unfolding disaster associated with a biological attack. Like community leaders, this group of medical responders must be aware of its own susceptibility to mental health sequelae and performance decrement as the increasing demands of disaster response outpace the availability of necessary resources. A bioterrorist attack will necessitate treatment of casualties who experience neuropsychiatric symptoms and syndromes. Although symptoms may result from exposure to infection with specific biological agents, similar symptoms may result from the mere perception of exposure or arousal precipitated by fear of infection, disease, suffering, and death. Conservative use of psychotropic medications may reduce symptoms in exposed and uninfected individuals, as may cognitive-behavioral interventions. Clear, consistent, accessible, reliable, and redundant information (received from trusted sources) will diminish public uncertainty about the cause of symptoms that might otherwise prompt persons to seek unnecessary treatment. Training and preparation for contingencies experienced in an attack have the potential to enhance delivery of care. Initiating supportive social, psychotherapeutic, and psychopharmacologic treatments judiciously for symptoms and syndromes known to accompany the traumatic stress response can aid the efficient treatment of some patients and reduce long-term morbidity in affected individuals. Preventive strategies and planning must take into account the idea that specific groups within the population are at higher risk for psychiatric morbidity. First responders comprise one group at psychologic risk in this situation, and healthcare providers comprise another. These and other high-risk groups will benefit from the same supportive interventions developed for the community as a whole.