ABSTRACT: Importance:Following clean (class I, not contaminated) surgical procedures, the rate of surgical site infection (SSI) should be less than approximately 2%. However, an infection rate of 12.2% has been reported following removal of orthopedic implants used for treatment of fractures below the knee. Objective:To evaluate the effect of a single dose of preoperative antibiotic prophylaxis on the incidence of SSIs following removal of orthopedic implants used for treatment of fractures below the knee. Design, Setting, and Participants:Multicenter, double-blind, randomized clinical trial including 500 patients aged 18 to 75 years with previous surgical treatment for fractures below the knee who were undergoing removal of orthopedic implants from 19 hospitals (17 teaching and 2 academic) in the Netherlands (November 2014-September 2016), with a follow-up of 6 months (final follow-up, March 28, 2017). Exclusion criteria were an active infection or fistula, antibiotic treatment, reimplantation of osteosynthesis material in the same session, allergy for cephalosporins, known kidney disease, immunosuppressant use, or pregnancy. Interventions:A single preoperative intravenous dose of 1000 mg of cefazolin (cefazolin group, n = 228) or sodium chloride (0.9%; saline group, n = 242). Main Outcomes and Measures:Primary outcome was SSI within 30 days as measured by the criteria from the US Centers for Disease Control and Prevention. Secondary outcome measures were functional outcome, health-related quality of life, and patient satisfaction. Results:Among 477 randomized patients (mean age, 44 years [SD, 15]; women, 274 [57%]; median time from orthopedic implant placement, 11 months [interquartile range, 7-16]), 470 patients completed the study. Sixty-six patients developed an SSI (14.0%): 30 patients (13.2%) in the cefazolin group vs 36 in the saline group (14.9%) (absolute risk difference, -1.7 [95% CI, -8.0 to 4.6], P = .60). Conclusions and Relevance:Among patients undergoing surgery for removal of orthopedic implants used for treatment of fractures below the knee, a single preoperative dose of intravenous cefazolin compared with saline did not reduce the risk of surgical site infection within 30 days following implant removal. Trial Registration:clinicaltrials.gov Identifier: NCT02225821.