Contrast media associated acute renal failure represents the third cause of in-hospital renal function deterioration after decreased renal perfusion and post-operative renal insufficiency. Although generally benign, this complication shows a mortality rate ranging from 3.8% to 64%, depending on the increase of creatinine concentration. The mechanism by which contrast-induced renal failure occurs is not well understood. Contrast agent-associated nephrotoxicity appears to be a result of direct contrast induced renal tubular epithelial cell toxicity and renal medullary ischemia. Furthermore, a key mechanism seems to be alteration in renal dynamics, probably caused by imbalances between vasodilator and vasoconstrictor factors, including the activities of nitric oxide, prostaglandins, endothelin and reactive oxygen species. Recommendations to prevent contrast-associated nephrotoxicity are: 1) periprocedural hydration, 2) use of a low osmolality contrast, and 3) limiting the amount of contrast agent. Recently, considerable interest has resulted from the preliminary positive data on the effectiveness of prophylactic administration of antioxidant compounds (such as acetylcysteine and ascorbic acid) and fenoldopam.