In the standard textbooks the staphylococcus is usually noted among other micro-organisms as a possible etiologic agent in the production of bronchopneumonia. A detailed description of the clinical picture of the disease associated with the presence of this organism in the lung has thus far failed to come to our attention. This is no doubt due in part to the relative rarity of this infection as encountered in civil practice, and possibly to the lack of careful study of the bacteriology of acute respiratory affections until but recently. How rarely Staphylococcus aureus infection of the lung occurs and how grave the prognosis is may best be stated by noting that in a series of about 800 cases of pneumonia, drawn from all classes of the population of New York City, only thirteen cases were treated at the hospital of the Rockefeller Institute under the direction of Dr. Rufus Cole, in