SURGEONS are called on to treat a number of infections which do not respond to the usual surgical measures or to the forms of chemotherapy that have been available. They are frequently complicated by the presence of intestinal fistulas, intestinal obstruction, urinary obstruction, pieces of dead bone, necrotic fascia or tendon and poor blood supply. Because of these factors and because several types of bacteria are usually present, it is difficult to compare these infections with one another or to classify them for purposes of evaluating therapy. In these respects, they differ significantly from such diseases as pneumococcic pneumonia, meningococcic meningitis, typhoid and gonococcic urethritis, all of which have a simple etiologic agent and run a fairly typical course. Examples of these infections can be found in any surgical service. They are usually difficult to treat, often persisting for many weeks. For these reasons it is important to search for