Infection is a major cause of morbidity and mortality following penetrating abdominal trauma. Antibiotics are routinely used although their effectiveness has never been evaluated in a placebo-controlled randomised trial, and they have never been shown to reduce the incidence of post injury intra-abdominal, as opposed to wound, infections. The available evidence indicates that a single preoperative dose of an appropriate antibiotic is adequate prophylaxis for penetrating abdominal injuries. Postoperative antibiotics should be reserved for "late" (> 12 hours) operations for enteric perforations. The optimal duration of treatment under these circumstances is not well established. Fever and leucocytosis are poor indicators of the need for continued postoperative administration in the severely traumatised patient.