Objective: To determine whether circular plastic wound edge protectors (CWEPs) significantly reduce the rate of surgical site infections (SSIs) in comparison to standard surgical towels in patients undergoing laparotomy. Background: SSIs cause substantial morbidity, prolonged hospitalization, and costs and remain one of themost frequent surgical complications. CWEPs have been proposed as a measure to reduce the incidence of SSIs. Methods: In this randomized controlled, multicenter, 2-arm, parallel-group design, patient-and observer-blinded trial patients undergoing open elective abdominal surgery were assigned to either intraoperative wound coverage with a CWEP or standard coverage with surgical towels. Primary endpoint was superiority of intervention over control in terms of the incidence of SSIs within a 30-day postoperative period. Results: Between September 2010 and November 2012, 608 patients undergoing laparotomy were randomized at 16 centers across Germany. Three patients in the device group and 11 patients in the control group did not undergo laparotomy. Patients' and procedural characteristics were well balanced between the 2 groups. Forty-eight patients discontinued the study prematurely, mainly because of relaparotomy (control, n = 9; intervention, n = 9) and death (control, n = 4; intervention, n = 7). A total of 79 patients experienced SSIs within 30 days of surgery, 27 of 274 (9.9%) in the device group and 52 of 272 (19.1%) in the control group (odds ratio = 0.462, 95% confidence interval: 0.281-0.762; P = 0.002). Subgroup analyses indicate that the effect could be more pronounced in colorectal surgery, and in cleancontaminated/contaminated surgeries. Conclusions: Our trial shows that CWEPs are effective at reducing the incidence of SSIs in elective and clean or clean-contaminated open abdominal surgery.