Infection is an important cause of late morbidity and mortality following traumatic injury. As part of a coordinated treatment effort for the injured patient, preventive antibiotic use can reduce subsequent infectious complications. Available evidence supports the use of antibiotic(s) with activity against both aerobic and anaerobic enteric pathogens for patients with penetrating abdominal injuries and bowel penetration. Patients with open fractures benefit from the use of an antibiotic with activity against Staphylococcus aureus. Data on the ideal dose and duration of antibiotic administration in these situations are incomplete. It is likely that the best results will be obtained with early parenteral administration of large doses of the chosen antibiotic continuing for less than or equal to 24 hours. For injuries other than penetrating abdominal wounds and open fractures, definitive information is not available.