There are many potential factors to consider in choosing (or comparing) an appropriate perioperative antibiotic regimen. One consideration is the infection rate at both the surgical site and remote sites, another is the potential development of antimicrobial resistance, a third consideration is cost, and yet another is the potential for adverse reactions to the antibiotic. Fonseca et al1 report the results of a “before-after” trial evaluating the rate of surgical site infection after changing from a 24-hour regimen to a single preoperative dose of cephazolin. The authors studied 12 299 patients in total, covering a wide range of surgical disciplines. They report an infection rate of 2.0% before and 2.1% after the change in their antibiotic protocol (P = .67).