Several cases of Legionnaires' disease occurred in a French hospital in 1982. Thirteen strains of a legionella-like organism with several unusual characteristics were subsequently isolated from the hospital hot water system. The various features of these strains show that they are identical to the new species 'Legionella anisa' described by the Centers for Disease Control. The possible pathogenicity of these strains to man and their relationship with the recently described Legionella bozemanii serogroup 2 are discussed.