Legionella pneumophila is an important cause of community-acquired pneumonia. Domestic sources of infection have been increasingly recognised among community-acquired cases. This report summarises the public health investigations and management of a single community-acquired case of Legionnaires' disease in Queensland, commenced in the context of a suspected outbreak. Legionellae from the case's domestic water supply were indistinguishable from the clinical isolate. The implications for future investigation of sporadic cases are discussed.