The development of perioperative acute renal failure is associated with a high incidence of morbidity and mortality. Although this incidence varies with different surgical procedures and with the definition used for renal failure, we now understand better the aetiology of the underlying problem. However, successful strategies to provide renal protection or strategies for 'rescue therapy' are either lacking, unsubstantiated by randomized clinical trials, or show no significant efficacy. The present review considers the physiology and pharmacology of the kidney; the characterization of tests of renal function; the cause of postoperative renal dysfunction; what is presently available for its prevention and treatment; and the effect of postoperative renal impairment on patient outcome.