Pseudomonas putrefaciens is an unusual cause of human disease. Since 1978 only five cases of bacteremia due to this organism have been reported. Within 12 recent months four cases of bacteremia due to P. putrefaciens were seen - two occurred in patients with chronic infections of a lower extremity, one in a patient with neutropenia, and one in a patient with fulminant septicemia and disseminated intravascular coagulation. Two of the patients had prostheses; in neither case did prosthetic infection or prosthetic failure occur. Two syndromes of bacteremic infection with P. putrefaciens are suggested. One syndrome is associated with chronic infection of a lower extremity, is fairly well tolerated, and responds to appropriate antimicrobial agents. The other syndrome is more fulminant and may be associated with severe underlying debility, liver disease, and malignancy. It is not yet known whether this is a meaningful distinction. The significance of the recent increase is the isolation of this organism is not clear at present.