Antibiotic prophylaxis consists of a brief course of antibiotics initiated preoperatively in order to decrease the risk of postoperative wound infection in the patient with a clean wound. The antibiotic should be started within 60 minutes before skin incision and continued for not more than 24 hours. Antibiotic therapy is indicated for the contaminated or dirty wound. In open fractures, antibiotics should be started as soon as possible after injury and continued for 3 days (type I and II fractures) or 5 days (type III). This treatment should be combined with local therapy consisting of antibiotic-impregnated polymethylmethacrylate beads. Although the utility of antibiotics in low-velocity gunshot wounds is controversial, high-velocity gunshot wounds should be treated with 48 to 72 hours of antibiotic therapy.