Information on the incidence and nature of the causative organisms in the infected tissues of patients with diabetic gangrene is scanty. Studies in which material for culture was obtained from the presenting lesion reveal multiple organisms in host isolates. No data are available regarding the bacterial flora of the deep infected tissue itself, uncontaminated by surface organisms. In this investigation 58 specimens from 52 patients were obtained utilizing aerobic and anaerobic culture techniques. In the surgical theater, material was obtained from the infected deep tissues using careful aseptic dissection techniques. All patients had been on antibiotic therapy from 2 to 10 days before the study. An average of 2.3 organisms per specimen was found. The predominant organisms were Proteus sp., Enterococcus, Staphylococcus aureus, and other enterobacteriacae in that order. Anaerobes were isolated in 27 per cent of cases, but never as the only organism. Prior antibiotic therapy did not eradicate infection in infected diabetic gangrene.