Inadvertent bacterial contamination of an anesthetic vaporizer poses a potential hazard if such bacteria are subsequently aerosolized and delivered to an anesthetic circuit. This remote hazard would be removed if the volatile anesthetic were itself bactericidal, or if any of the gases flowing through the vaporizer (e.g. nitrous oxide) were bactericidal. Accordingly, we have determined the survival characteristics both of several respiratory pathogens in enflurane and of the sturdiest of those pathogens in other anesthetics. The bacteria were selected for their relative frequency in postoperative patients.