A Legionella-like organism (strain 1087-AZ-H) was isolated from a pleural-fluid specimen from a renal transplant patient undergoing immunosuppressive therapy. Growth characteristics and gas-liquid chromatography profiles of the isolate were consistent with those for Legionella spp. The isolate fluoresced blue-white under long-wave UV light. Strain 1087-AZ-H was serologically distinct in the slide agglutination test with absorbed antisera. DNA hybridization studies placed it in a new Legionella species, Legionella tucsonensis (ATCC 49180).