Acute renal failure (ARF) is a common and important complication of critical illness and many interventions have been proposed to prevent it. The pathogenesis of acute renal failure during critical illness is poorly understood. Animal models are based on the induction of renal ischemia and do not reflect the dominance of sepsis as a cause of ARF in the clinical arena. Although biological rationale exists for several interventions, none have been shown to be effective in large randomized double-blind multicentre trials. The only interventions with close to level I evidence are confined to the attenuation of radiocontrast nephropathy. The effect on such interventions is, however, of limited clinical relevance to critically ill patients. The maintenance of adequate intravascular filling, cardiac output and renal perfusion pressure and the avoidance of hypoxemia, marked anemia and nephrotoxins remain the only justifiable interventions at this time.