Objective: The Working Group on Civilian Biodefense has developed consensus-based recommendations for measures to be taken by medical and public health professionals if tularemia is used as a biological weapon against a civilian population. Participants: The working group included 25 representatives from academic medical centers, civilian and military governmental agencies, and other public health and emergency management institutions and agencies. Evidence: MEDLINE databases were searched from January 1966 to October 2000, using the Medical Subject Headings Francisella tularensis, Pasteurella tularensis, biological weapon, biological terrorism, bioterrorism, biological warfare, and biowarfare. Review of these references led to identification of relevant materials published prior to 1966. In addition, participants identified other references and sources. Consensus Process: Three formal drafts of the statement that synthesized information obtained in the formal evidence-gathering process were reviewed by members of the working group. Consensus was achieved on the final draft. Conclusions: A weapon using airborne tularemia would likely result 3 to 5 days later in an outbreak of acute, undifferentiated febrile illness with incipient pneumonia, pleuritis, and hilar lymphadenopathy. Specific epidemiological, clinical, and microbiological findings should lead to early suspicion of intentional tularemia in an alert health system; laboratory confirmation of agent could be delayed. Without treatment, the clinical course could progress to respiratory failure, shock, and death. Prompt treatment with streptomycin, gentamicin, doxycycline, or ciprofloxacin is recommended. Prophylactic use of doxycycline or ciprofloxacin may be useful in the early postexposure period.