The case to be presented is unique for several reasons. It is the first case of osteomyelitis due to Bacillus pyocyaneus to be reported in the literature. It is the only case of spinal skeletal involvement by this organism which could be found. Finally, it is one of the few cases in which sulfanilamide therapy was tried and appeared effective. The literature on infections due to B. pyocyaneus (Pseudomonas aeruginosa) has been reviewed in detail in several papers in the past twenty-five years.1No effort will be made to repeat this work. The organism is not uncommonly encountered in infected wounds of various types, especially large granulating areas. Ordinarily it is only slightly pathogenic, is easily controlled by applications of boric acid and presents no problem. It is recognizable by its color and odor. Occasionally, however, it becomes a dangerous pathogen, invading visceral cavities, mucous membranes and even the