Although antibiotics are widely used in an attempt to decrease the incidence of infections after facial fractures, no systematic prospective study of their efficacy has been performed. In this study, all adult patients with facial fractures who had not received antibiotics were asked to participate in a clinical trial. There were 101 patients with facial fractures enrolled into the study and randomized prospectively into two groups. One group received no antibiotics. The other group received cefazolin sodium, 1 g intravenously, one hour prior to the surgical procedure, and a similar dose eight hours later. Of the 101 patients enrolled in the study, 79 had mandibular fractures, 18 had zygoma fractures, and four had Le Fort fractures. When all facial fractures were considered, perioperative intravenous cefazolin reduced the incidence of postoperative infections; 42.2% in the no-antibiotic group became infected, and 8.9% in the antibiotic group became infected. On the basis of this study, we conclude that cefazolin, used perioperatively, diminished the incidence of postoperative infections in facial fractures.