Dexamethasone is widely used by anaesthetists in the perioperative period, principally as an effective antiemetic to prevent postoperative nausea and vomiting (PONV). The molecular mechanisms underlying dexamethasone’s antiemetic action are not fully understood. However, because it is a potent glucocorticosteroid, it is has immunosuppressive and hyperglycaemia effects. It is hypothesised that these actions may increase the risk of perioperative infections, particularly in patients with diabetes mellitus, who are already at increased risk of complications. Whether the use of dexamethasone in the perioperative period increases the risk of surgical site and other infections, has not been definitively established. This is an important health priority as in Australia alone up to one million patients will receive dexamethasone as part of their anaesthesia care annually. This study aims to definitively address the impact of dexamethasone on surgical site infection and will be stratified according to diabetes status.