Pneumonia is one of the principal manifestations of Q fever, a disease caused by Coxiella burnetii. This bacterium can replicate only within cells, yet it is capable of surviving in the environment because it can withstand drying and substantial temperature variations. Livestock, especially sheep, goats and cattle, are a major reservoir of C burnetii. The organism is transmitted to humans by direct contact with animal products, especially during parturition. Aerosols have transmitted infection over considerable distances. The illness is characterized by an influenza-like syndrome with patchy pulmonary infiltrates. The pneumonia may be accompanied by biochemical evidence of mild hepatitis. The diagnosis is established serologically. Tetracycline or doxycycline provide effective therapy.