Perioperative acute kidney injury (AKI) is not uncommon and is associated with considerable morbidity and mortality. Recently, several definition systems for AKI were proposed, incorporating both small changes of serum creatinine and urinary output reduction as diagnostic criteria. Novel biomarkers are under investigation as fast and accurate predictors of AKI. Several special considerations regarding the risk of AKI are of note in the surgical patient. Co-morbidities are important risk factors for AKI. The surgery in itself, especially emergency and major surgery in the critically ill, is associated with a high incidence of AKI. Certain types of surgeries, such as cardiac and transplantation surgeries, require special attention because they carry higher risk of AKI. Nephrotoxic drugs, contrast dye, and diuretics are commonly used in the perioperative period and are responsible for a significant amount of in-hospital AKI. Before surgery, the anaesthetist is required to identify patients at risk of AKI, optimize anaemia, and treat hypovolaemia. During surgery, normovolaemia is of utmost importance. Additionally, the surgical and anaesthesia team is advised to use measures to reduce blood loss and avoid unnecessary blood transfusion. Hypotension should be avoided because even short periods of mean arterial pressure <55-60 mm Hg carry a risk of postoperative AKI. Higher blood pressures are probably required for hypertensive patients. Urine output can be reduced significantly during surgery and is unrelated to perioperative renal function. Thus, fluids should not be given in excess for the sole purpose of avoiding or treating oliguria. Use of hydroxyethyl starch needs to be reconsidered. Recent evidence indicates a beneficial effect of administering low-chloride solutions.