Members of the Legionella genus are ubiquitous aquatic bacteria and the etiologic agents of Legionnaires' disease, a potentially fatal form of pneumonia. Using the chrome azurol S (CAS) assay, we previously determined that Legionella pneumophila secretes a siderophore (legiobactin) when it is,grown in a low-iron, chemically defined medium (CDM). In the present study, we examined 29 other species of Legionella for their ability to produce CAS-reactive material when grown in deferrated CDM. Although some of the species did not grow in CDM, the majority replicated and secreted CAS reactivity, suggesting that siderophores are conserved among the legionellae.