Coxiella burnetii, which causes Q fever, is a highly infectious agent that is widespread among livestock around the world. Although the culture process for coxiella is laborious, large amounts of infectious material can be produced. If used as an aerosolised biological weapon, coxiella may not cause high mortality, but could provoke acute disabling disease. In its late course, Q fever can be complicated by fatal (eg, endocarditis) or debilitating (eg, chronic fatigue syndrome) disorders. The diagnosis of Q fever might be delayed because of non-specific and protean presentations. Effective antibiotic treatment is available for the acute form of disease but not for the chronic complications. Vaccination and chemoprophylaxis in selected individuals may be used in the event of bioterrorism.