A 46-year-old man showed a clinical response when treated with parenteral erythromycin for what was initially thought to be legionnaires' disease, but an organism isolated from his pleural fluid on CYE agar was subsequently identified as Francisella tularensis. Tularemia should be suspected in all cases of atypical pneumonia in the appropriate setting. Erythromycin may be effective empiric therapy in such cases. Because of the possibility of inadvertent isolation of Francisella tularensis on CYE agar, all cultures for suspected Legionella should be handled with extreme caution, preferably in a biological hood.