Acute renal failure (ARF) is an abrupt decline of renal function, and acute tubular necrosis (ATN) is its more frequent expression. Recent contributions in physiopathological knowledge, specially in post-ischemic ARF, are scarcelly reflected in therapy. Morbidity and mortality due to ARF are very high, mainly in critically ill patients. Prevention and treatment of ATN are based in avoiding nephrotoxicity and renal ischemia. An adequate evaluation of renal risk factors in hospitalized patients is important. Maintaining euvolemia, effective cardiac output and adequate renal perfussion pressure are three paramount factors in ischemia prevention. The best dialytic schedule is not universally accepted. ARF replacement therapy must be flexible, tailoring techniques (IHD, SLED, CRRT) to the clinical situation of patients. There is not a consensus in dialysis dose in ARF. Nevertheless, despite a robust scientific evidence is lacking, some data suggest that a delivered minimum dose of sKtV >1 in IHD or >35 ml/kg/h in CRRT would be beneficial for patient survival.