We previously described a rare case of native valve endocarditis due to a novel Legionella strain . The strain, designated H63T, was isolated from resected aortic valve tissue of a patient requiring aortic valve replacement for treatment of congestive heart failure related to infective native valve endocarditis. Sequencing of the 16S rRNA gene and preliminary BLAST analysis suggested that the strain represented either a novel clinical strain of Legionella brunensis or a novel Legionella species . L. brunensis was first isolated from cooling tower water in Czechoslovakia and has been isolated once from a case of Legionnaires’ disease in Europe . Based on DNA–DNA hybridization values of less than 70 % and sequence analysis of multiple gene targets, we now report that H63T represents a novel Legionella species. Phenotypic profiling revealed a number of differences between H63T and its phylogenetically nearest neighbours. Furthermore, H63T replicated in a human macrophage cell line and in the murine lung, indicating that H63T represents a virulent strain.