Legionella pneumophila is considered as a relatively common cause of pneumonia characterized by high mortality rate. Microbiological diagnosis of Legionnaires’disease includes a wide variety of methods such as culture, direct fluorescent antibody staining (DFA), serum antibody (IFA) testing and Legionella urinary antigen testing. The reported sensitivities of these methods vary widely. Detection of Legionella urinary antigen by the immunochromatographic assay ICT Binax Now Legionella Urinary Antigen is considered a successful alternative to culture. There are no reports on the applicability of this test to specimens other than urine, in recent literature with an exception of a BAL positive ICT Binax Legionella antigen result. We present a case of an 18 year old girl with severe community-acquired pneumonia in whom diagnosis was mainly based on the detection of Legionella antigen in pleural fluid by the method of ICT Binax. Detection of Legionella antigen in pleural fluid by this particular method is the first described in literature, while a single case of detection of Legionella antigen in pleural fluid has been described in 1991 using RIA method. Pneumon 2004, 17(3):332-335.