In the last ten years anaerobic organisms have emerged as the major infecting agent in surgical patients. While these groups of organisms including Bacteroides fragilis, clostridia, and anaerobic cocci persist, there has, in addition, developed in the last few years a virulent group of nosocomial infections, and modern management of sepsis is primarily directed at gram-negative and anaerobic infections, which include nosocomial infections, for example, those caused by the Serratia group. Much has been learned about control of infections from the patient who has sustained thermal injury. While topical water-soluble antibiotics have been a remarkable advance in the care of the burn patient, systemic and subeschar antibiotics have proved essential in the management of severe burn injury. There is increasing evidence that there is remarkable interference with host defense mechanisms in patients who have sustained burns or significant trauma or intraabdominal infection. The patient sustaining nonthermal traumatic injury also sustains reduction in host resistance. Because of this and the additional initial contamination, in the traumatized patient antibiotic therapy should be started early and as a therapeutic measure. Newer localization techniques, including sonography and computed axial tomography scanning, have helped localize abdominal infections early. Specific antimicrobial therapy may be begun as an adjunct to the surgical therapy of intra-abdominal infection.