This systematic review includes 11 randomized, controlled trials of mixed patient groups, including patients with or without breast cancer. Studies were included in the review only if data from patients with breast cancer could be separated from patients without breast cancer. The intervention included pre- or perioperative antibiotics used as prophylaxis for the surgery. A range of antibiotic regimens were assessed in the 11 studies, and 5 of the studies defined a similar antibiotic strategy. Five of the studies had similar choice of antibiotic, type of surgery, and length of follow-up. The reviewers excluded 27 studies because of design and data collection not matching the review requirements.