Endogenous contamination from perforation or rupture of the gastrointestinal tract; exogenous contamination from missiles, knives, or invasive lines and tubes; and immunodepression related to the severity of injury are responsible for the increased infectious complications noted in patients who have undergone laparotomy for abdominal trauma. Perioperative use of clindamycin and an aminoglycoside, a second- or third-generation cephalosporin, or an enhanced-spectrum penicillin is clearly beneficial in lowering the incidence of intra-abdominal and wound infections. A 12- to 48-hour length of administration of antibiotics after operation is as effective as regimens of longer duration, although presently used dosages may be inadequate in severely injured patients. Adjunctive surgical maneuvers such as peritoneal irrigation with saline-containing antibiotic(s) remain controversial. Perioperative use of antibiotic prophylaxis, coupled with early operation and appropriate surgical technique, results in a 4.4% rate of intra-abdominal abscesses and a 5.1% rate of wound infections after laparotomy for abdominal trauma in modern trauma centers.